-
Police officers with their guns drawn hear the second explosion down the street. The first explosion knocked down a runner at the finish line of the 117th Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images)
-
Newspapers are on sale at a stand on Newbury Street on April 16, 2013 in Boston, Massachusetts. Security is especially tight in the city of Boston after two explosions went off near the finish of the Marathon, killing three people and injuring at least 141 others. Darren McCollester / Getty Images)
-
Some photos in this slideshow are graphic and may be disturbing to some viewers.
-
In this photo provided by The Daily Free Press and Kenshin Okubo, people react to an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (Kenshin Okubo / The Daily Free Press / AP)
-
-
A woman kneels and prays at the scene of the first explosion on Boylston Street near the finish line of the 117th Boston Marathon on April 15, 2013. (John Tlumacki / The Boston Globe / Getty Images)
-
Victims are in shock and being treated at the scene of the first explosion that went off near the finish line of the Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images)
-
People tend to an injured woman on the corner of Exeter and Newbury Streets after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Bill Greene / The Boston Globe / Getty Images)
-
Bystanders help an injured woman at the scene of the first explosion on Boylston Street near the finish line of the 117th Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images)
-
Medical workers runs an injured man past the finish line the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (Charles Krupa / AP)
-
Police and federal officials exit an apartment complex at 364 Ocean Avenue with a possible connection to the earlier expolsions during the Boston Marathon on April 15, 2013 in Revere, Massachusetts. Three people are confirmed dead and at least 141 injured after two explosions went off near the finish line to the marathon. (Darren McCollester / Getty Images)
-
A victim of the first explosion is helped on the sidewalk of Boylston Street, after two explosions went off near the finish line of the 117th Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images)
-
Unclaimed finish line bags are viewed near the scene of a twin bombing at the Boston Marathon, on April 16, 2013 in Boston, Massachusetts. Three people are confirmed dead and at least 141 injured after the explosions went off near the finish line of the marathon yesterday. The bombings at the 116-year-old Boston race, resulted in heightened security across the nation with cancellations of many professional sporting events as authorities search for a motive to the violence. (Spencer Platt / Getty Images)
-
A heavily armed Boston police officer (R) and a National Guard soldier (L) stands guard in front of the Taj Hotel April 16, 2013 in Boston, Massachusetts, in the aftermath of two explosions that struck near the finish line of the Boston Marathon April 15. A massive probe was underway Tuesday after two bombs struck the Boston Marathon, killing at least three and wounding more than 100. Monday's blasts near the finishing line raised fears of a terrorist attack more than a decade after nearly 3,000 people were killed in suicide airliner strikes on New York, Washington and Pennsylvania on September 11, 2001. US President Barack Obama went on national television to warn against "jumping to conclusions" but a senior White House official, speaking on condition of anonymity, said such an attack was "clearly an act of terror." (Stan Honda / AFP / Getty Images)
-
A man comforts a victim on the sidewalk at the scene of the first explosion near the finish line of the 117th Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images
-
Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (David L. Ryan / The Boston Globe / Getty Images)
-
Boston Police look at blown out windows at the scene of the first explosion on Boylston Street near the finish line of the Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images)
-
BOSTON - APRIL 15: Police officers with their guns drawn hear the second explosion down the street. The first explosion knocked down a runner at the finish line of the 117th Boston Marathon. (Photo by John Tlumacki/The Boston Globe via Getty Images)
-
-
Injured people lie on the sidewalk near a barrier at the scene of the first explosion that went off near the finish line of the 117th Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images)
-
BOSTON - APRIL 15: Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
Passersby put pressure on a victim's leg to try to stop the bleeding at the scene of the first explosion near the finish line of the Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images)
-
The marathon finish line bridge is seen on Boylston Street on April 16, 2013 in Boston, Massachusetts. on April 16, 2013 in Boston, Massachusetts. Security is especially tight in the city of Boston after two explosions went off near the finish of the Marathon, killing three people and injuring at least 141 others. (Darren McCollester / Getty Images)
-
Blood from victims covers the sidewalk on Boylston Street, at the site of an explosion during the 2013 Boston Marathon in Boston, Monday, April 15, 2013. At the right foreground is a folding chair with the design of an American flag on the cover. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (Charles Krupa / AP)
-
A runner reacts near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Alex Trautwig / Getty Images)
-
BOSTON - APRIL 15: (EDITOR'S NOTE: THIS IMAGE CONTAINS GRAPHIC CONTENT) A person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene in a wheelchair. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
A runner passes a police officer dressed in tactical gear, who blocks a road leading to the Boston Marathon route, the morning after explosions killed three and injured more than 140 in Boston, Tuesday, April 16, 2013. The bombs that blew up seconds apart at the finish line of one of the world's most storied races left the streets spattered with blood and glass, and gaping questions of who chose to attack at the Boston Marathon and why. (Charles Krupa / AP)
-
A person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene in a wheelchair. (David L. Ryan / The Boston Globe / Getty Images)
-
Carlos Arredondo, who was at the finish line of the 117th Boston Marathon when two explosives detonated, leaves the scene on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 28 injured after at least two explosions went off near the finish line to the marathon. (Darren McCollester / Getty Images)
-
BOSTON - APRIL 15: (EDITOR'S NOTE: THIS IMAGE CONTAINS GRAPHIC CONTENT) A person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene on a stretcher. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
Officials react as the first explosion goes off on Boylston Street near the finish line of the 117th Boston Marathon on April 15, 2013. (John Tlumacki / The Boston Globe / Getty Images)
-
First responders tend to the wounded after two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. (Kelvin Ma / Bloomberg / Getty Images)
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
BOSTON - APRIL 15: Two officials run away from the first explosion, right, on Boylston Street at the 177th Boston Marathon, April 15, 2013. (Photo by John Tlumacki/The Boston Globe via Getty Images)
-
A person who was injured in the first explosion is wheeled across the finish line of the Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images)
-
BOSTON - APRIL 15: (EDITOR'S NOTE: THIS IMAGE CONTAINS GRAPHIC CONTENT) A person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene on a stretcher. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
-
Neighbors hug outside the home of the Richard family in the Dorchester neighborhood of Boston, Tuesday, April 16, 2013. Martin Richard, 8, was killed in Mondays bombing at the finish line of the Boston Marathon. (Michael Dwyer / AP)
-
First responders rush to help injured people after two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. (Kelvin Ma / Bloomberg / Getty Images)
-
Emergency workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. (AP Photo/Charles Krupa)
-
There was smoke and panic in the street as emergency personnel responded to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (David L. Ryan / The Boston Globe / Getty Images)
-
BOSTON - APRIL 15: (EDITOR'S NOTE: THIS IMAGE CONTAINS GRAPHIC CONTENT) A person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene on a stretcher. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
A Boston police officer wheels in injured boy down Boylston Street as medical workers carry an injured runner following an explosion during the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria at the marathon's finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
BOSTON - APRIL 15: Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: A man lays on the ground after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: Two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
Medical workers wheel the injured across the finish line during the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
An unidentified Boston Marathon runner, center, is reunited with loved ones near Copley Square following an explosion in Boston Monday, April 15, 2013. (AP Photo/Winslow Townson)
-
Medical responders run an injured man past the finish line the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. (AP Photo/Charles Krupa)
-
A Boston police officer clears Boylston Street following an explosion at the finish line of the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria at the finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
A second explosion goes off (rear) as a runner was blown to the ground by the first explosion near the finish line of the 117th Boston Marathon. (John Tlumacki / The Boston Globe / Getty Images)
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. (Kelvin Ma / Bloomberg / Getty Images)
-
Investigators shine flashlights at one of the blast sites on Boylston Street near the finish line of the 2013 Boston Marathon in the wake of two blasts in Boston Monday, April 15, 2013. (AP Photo/Elise Amendola)
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. (Kelvin Ma / Bloomberg / Getty Images)
-
-
First responders tend to the wounded where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. (Kelvin Ma / Bloomberg / Getty Images)
-
Runners and spectators flee from the scene where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. (Kelvin Ma / Bloomberg / Getty Images)
-
First responders tend to the wounded where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. (Kelvin Ma / Bloomberg / Getty Images)
-
A man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Jim Rogash / Getty Images)
-
A runner embraces another woman near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Alex Trautwig / Getty Images)
-
Massachusetts State Police guard an area near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Alex Trautwig / Getty Images)
-
Police and runners stand near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 28 injured after at least two explosions went off near the finish line to the marathon. (PAlex Trautwig / Getty Images)
-
A woman looks at the blood on her hands as she is loaded into an ambulance after being injured after two bombs exploded on the marathon route on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Jim Rogash / Getty Images)
-
In this photo provided by The Daily Free Press and Kenshin Okubo, people assist an injured after an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (Kenshin Okubo / The Daily Free Press / AP)
-
In this photo provided by The Daily Free Press and Kenshin Okubo, people help an injured person after an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (Kenshin Okubo / The Daily Free Press / AP)
-
In this handout provided by the White House, U.S. President Barack Obama (L) talks on the phone with FBI Director Robert Mueller to receive an update on the explosions that occurred in Boston, in the Oval Office of the White House, April 15, 2013 in Washinton, DC. Seated with the President are Lisa Monaco, Assistant to the President for Homeland Security and Counterterrorism, and Chief of Staff Denis McDonough. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Pete Souza / The White House / Getty Images)
-
Beacon Street near Kenmore Square remains empty for the use of emergency vehicles after two explosive devices detonated at the finish line of the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Alex Trautwig / Getty Images)
-
Boston police officers keep a perimeter secure in Boston's Copley Square, Tuesday, April 16, 2013 as an investigation continues into the bomb blasts at the finish area of the Boston Marathon which killed 3 and injured over 140 people. (AP Photo/Elise Amendola)
-
Karen Kaye, right, communications and community relations director for Big Peach Running Co., embraces Reginald Bohannon, of Atlanta, before the start of an organized moment of silence and memorial run to show solidarity with victims of the Boston Marathon bombing, Tuesday, April 16, 2013, in Atlanta. The explosions Monday afternoon killed at least three people and injured more than 140. (AP Photo/David Goldman)
-
-
-
In this image from video provided by Ryan Hoyme, the second explosion can be seen in the distance as smoke from the first explosion surrounds spectators exiting the stands during the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Ryan Hoyme)
-
-
-
-
Rescue personnel aid injured people near the finish line of the 2013 Boston Marathon following explosions in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Herald, Stuart Cahill)
-
President Barack Obama leaves the podium after speaking in the James Brady Press Briefing Room at the White House in Washington, Monday, April 15, 2013, following the explosions at the Boston Marathon. (AP Photo/Charles Dharapak)
-
Firefighters tend to a man following an explosion at the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. Two bombs exploded at the Boston Marathon finish line Monday killing at least two people injuring dozens. (AP Photo/Michael Dwyer)
-
One of the blast sites on Boylston Street near the finish line of the 2013 Boston Marathon is investigated by two people in protective suits in the wake of two blasts in Boston Monday, April 15, 2013. (AP Photo/Elise Amendola)
-
-
-
-
A solitary runner heads down the banks of the Charles River in Cambridge, Mass., in front of the Boston skyline, at dawn the morning after explosions killed three and injured more than 140 at the Boston Marathon, Tuesday, April 16, 2013. The bombs that blew up seconds apart at the finish line of one of the world's most storied races left the streets spattered with blood and glass, and gaping questions of who chose to attack at the Boston Marathon and why. (Charles Krupa / AP)
-
In this photo provided by The Daily Free Press and Kenshin Okubo, people react to an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Daily Free Press, Kenshin Okubo) MANDATORY CREDIT
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion Monday, April 15, 2013 in Boston. Two bombs exploded near the finish line of the marathon on Monday, killing at least two people, injuring at least 22 others and sending authorities rushing to aid wounded spectators. (AP Photo/Charles Krupa)
-
Boston police clear an area following an explosion near the finish line of the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
Medical personnel work outside the medical tent in the aftermath of two blasts which exploded near the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Elise Amendola)
-
Medical workers aid an injured woman at the finish line of the 2013 Boston Marathon following two explosions there, Monday, April 15, 2013 in Boston. Two bombs exploded near the finish of the Boston Marathon on Monday, killing at least two people, injuring at least 23 others and sending authorities rushing to aid wounded spectators. (AP Photo/Charles Krupa)
-
Workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Herald, Stuart Cahill) MANDATORY CREDIT
-
In this photo provided by The Daily Free Press and Kenshin Okubo, people react to an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Daily Free Press, Kenshin Okubo) MANDATORY CREDIT
-
In this photo provided by The Daily Free Press and Kenshin Okubo, people react to an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Daily Free Press, Kenshin Okubo) MANDATORY CREDIT
-
Medical workers aid an injured woman at the scene of a bomb blast near the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two bombs exploded near the finish line of the Boston Marathon on Monday, killing at least two people and injuring at scores of others (AP Photo/Charles Krupa)
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two bombs exploded near the finish line of the Boston Marathon on Monday, killing at least two people and injuring dozens of others (AP Photo/Charles Krupa)
-
Runners who were diverted from the race course walk on the Commonwealth Mall two blocks from the site of an explosion at the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. Two bombs exploded near the finish line of the Boston Marathon on Monday, killing at least two people and injuring at least 23 others. (AP Photo/Michael Dwyer)
-
Una mujer llora afectada por una explosión mientras caminan cerca de la línea de meta de la Maratón de Boston el lunes 15 de abril de 2013. Dos bombas estallaron el lunes causando la muerte de dos personas y heridas a otras 50, informó la Policía de Boston. (AP Foto/Josh Reynolds)
-
An armed FBI agent passes a Boston police officer following an explosion at the finish line of the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Josh Reynolds)
-
A firefighter tends to an injured man following an explosion near the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Michael Dwyer)
-
One of the blast sites on Boylston Street near the finish line of the 2013 Boston Marathon is investigated by a person in a protective suit in the wake of two blasts in Boston, Monday, April 15, 2013. (AP Photo/Elise Amendola)
-
Firefighters tend to a man following an explosion at the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. Two bombs exploded at the Boston Marathon finish line Monday killing at least two people injuring dozens. (AP Photo/Michael Dwyer)
-
In this photo provided by The Daily Free Press and Kenshin Okubo, people react to an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Daily Free Press, Kenshin Okubo) MANDATORY CREDIT
-
Two people walk down the sidewalk as Boston police clear the area in Copley Square in the aftermath of two blasts which exploded near the finish line of the Boston Marathon in Boston Monday, April 15, 2013. The explosions Monday killed at least two people and injured dozens. (AP Photo/Elise Amendola)
-
This photo provided by Bruce Mendelsohn shows the scene after two explosions occurred during the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/ Bruce Mendelsohn) MANDATORY CREDIT
-
Medical workers respond following an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Globe, David L Ryan) MANDATORY CREDIT
-
Boston police direct runners who were diverted from the race course following an explosion at the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Michael Dwyer)
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Globe, David L Ryan) MANDATORY CREDIT
-
Medical workers aid injured people at the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Globe, David L Ryan) MANDATORY CREDIT
-
Chris Darmody, right, holds his wife Sue in Boston, Monday, April 15, 2013. Chris says he was waiting for Sue when an explosion detonated near his location at the finish line of the Boston Marathon. The couple were later reunited after all runners were diverted from the course. (AP Photo/Michael Dwyer)
-
Emergency responders comfort a woman on a stretcher who was injured in a bomb blast near the finish line of the Boston Marathon Monday, April 15, 2013 in Boston. Two bombs exploded in the packed streets near the finish line of the marathon on Monday, killing at least two people and injuring more than 80, authorities said. (AP Photo/Jeremy Pavia)
-
Emergency responders aid a woman on a stretcher who was injured in a bomb blast near the finish line of the Boston Marathon Monday, April 15, 2013 in Boston. Two bombs exploded in the packed streets near the finish line of the marathon on Monday, killing at least two people and injuring more than 80, authorities said. (AP Photo/Jeremy Pavia)
-
Emergency responders comfort a woman on a stretcher who was injured in a bomb blast near the finish line of the Boston Marathon Monday, April 15, 2013 in Boston. Two bombs exploded in the packed streets near the finish line of the marathon on Monday, killing at least two people and injuring more than 80, authorities said. (AP Photo/Jeremy Pavia)
-
Rescue personnel aid injured people near the finish line of the 2013 Boston Marathon following explosions in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Herald, Stuart Cahill)
-
Rescue personnel aid injured people near the finish line of the 2013 Boston Marathon following explosions in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Herald, Stuart Cahill)
-
Injured people and debris lie on the sidewalk near the Boston Marathon finish line following an explosion in Boston, Monday, April 15, 2013. (AP Photo/MetroWest Daily News, Ken McGagh) MANDATORY CREDIT
-
As Boston Marathon runners walk by, SWAT team members stand guard near the finish line in Boston Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. ( (AP Photo/Winslow Townson)
-
People react to an explosion at the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Herald, Stuart Cahill) BOSTON GLOBE OUT; METRO BOSTON OUT; MAGS OUT;
-
Investigators shine flashlights at one of the blast sites on Boylston Street near the finish line of the 2013 Boston Marathon in the wake of two blasts in Boston Monday, April 15, 2013. (AP Photo/Elise Amendola)
-
In this image from video provided by Ryan Hoyme, the second explosion can be seen in the distance as smoke from the first explosion surrounds spectators exiting the stands during the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Ryan Hoyme)
-
Bill Iffrig, 78, lies on the ground as police officers react to a second explosion at the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. Iffrig, of Lake Stevens, Wash., was running his third Boston Marathon and near the finish line when he was knocked down by one of two bomb blasts. (AP Photo/The Boston Globe, John Tlumacki)
-
A Boston Marathon runner leaves the course crying near Copley Square following an explosion at the finish line in Boston on Monday, April 15, 2013. (AP Photo/Winslow Townson)
-
People react as an explosion goes off near the finish line of the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions went off at the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Globe, David L Ryan) MANDATORY CREDIT
-
BOSTON, MA - APRIL 15: A runner embraces another woman on the marathon route near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images)
-
BOSTON, MA - APRIL 15: A runner reacts near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images)
-
BOSTON, MA - APRIL 15: A runner embraces another woman near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images)
-
BOSTON, MA - APRIL 15: A woman is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images)
-
BOSTON, MA - APRIL 15: A woman is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images)
-
BOSTON, MA - APRIL 15: A woman, with blood on fingers, is loaded into an ambulance after being injured after two bombs exploded on the marathon route on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images)
-
BOSTON, MA - APRIL 15: A woman is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images)
-
BOSTON, MA - APRIL 15: Two blood stained feet of a man hang outside an ambulance outside a medical tent located near the finish of the 117th Boston Marathon after two bombs exploded on the marathon route on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images)
-
Boston police ask people to leave the area in Copley Plaza in the aftermath of two blasts which exploded near the finish line of the Boston Marathon in Boston Monday, April 15, 2013. (AP Photo/Elise Amendola)
-
Paramédicos asisten a un hombre herido después de una explosión en Boston el Lunes 15 de Abril de 2013. Dos bombas estallaron cerca de la línea de meta del maratón de Boston, causaron dos muertos y 22 heridos, dijeron la policía y los organizadores de la competición. (AP Foto/The Boston Globe, David L. Ryan)
-
Uniformed Division Secret Service officers stand watch on the sidewalk in front of the White House looking north from Pennsylvania Avenue during heightened security following the explosions in Boston, Monday, April 15, 2013 in Washington. (AP Photo/Charles Dharapak)
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions near the finish of the Boston Marathon on Monday, killing at least two people, injuring over 20 others. (AP Photo/Charles Krupa)
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
An unidentified Boston Marathon runner is comforted as she cries in the aftermath of two blasts which exploded near the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. (AP Photo/Elise Amendola)
-
First responders transport an injured woman in a wheelchair where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders transport the wounded where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders rush to help injured people after two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
BOSTON - APRIL 15: People on Boylston Street check their mobile devices for news of the explosions near the finish line at the 117th Boston Marathon. (Photo by Jim Davis/The Boston Globe via Getty Images)
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
BOSTON - APRIL 15: (EDITOR'S NOTE: THIS IMAGE CONTAINS GRAPHIC CONTENT) A person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene on a stretcher. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
Boston Police cordon off the finish line area where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
BOSTON - APRIL 15: (EDITOR'S NOTE: THIS IMAGE CONTAINS GRAPHIC CONTENT) Destruction and injured people at the site of the one of the explosions that went off near the finish line of the 117th Boston Marathon. Barricades hindered the EMS from getting to the injured. (Photo by John Tlumacki/The Boston Globe via Getty Images)
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
BOSTON, MA - APRIL 15: A man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images)
-
BOSTON - APRIL 15: (EDITOR'S NOTE: THIS IMAGE CONTAINS GRAPHIC CONTENT) Injured people lie on the sidewalk near a barrier at the scene of the first explosion that went off near the finish line of the 117th Boston Marathon. (Photo by John Tlumacki/The Boston Globe via Getty Images)
-
First responders tend to the wounded where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders tend to the wounded where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
Runners and spectators flee from the scene where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders tend to the wounded where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders tend to the wounded where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders load injured people into an ambulance where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders tend to the wounded, including a young boy in a wheelchair, where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
Firemen carry an injured person where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
A runner with bloodstains on his body walks away from the scene where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
BOSTON, MA - APRIL 15: A man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images)
-
BOSTON, MA - APRIL 15: A man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images)
-
BOSTON, MA - APRIL 15: A man is loaded into an ambulance after he was injured by one of two bombs exploded during the 117th Boston Marathon near Copley Square on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Jim Rogash/Getty Images)
-
BOSTON - APRIL 15: A Boston Marathon runner wanders through traffic at Boylston Street and Massachusetts Avenue after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by Jim Davis/The Boston Globe via Getty Images)
-
BOSTON, MA - APRIL 15: A member of the bomb squad investigates a suspicious item on the road near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images)
-
BOSTON - APRIL 15: Two men look under bleachers for another device after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON, MA - APRIL 15: A member of the bomb squad investigates a suspicious item on the road near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images)
-
BOSTON - APRIL 15: Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: A second explosion goes off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: State Police cruisers sped toward Copley Place after two explosions downtown near the finish line of the 117th Annual Boston Marathon in Boston, Mass. on Monday, April 15, 2013. (Photo by Yoon S. Byun/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: Runners who had not finished the race were stopped before the Massachusetts Avenue overpass on Commonwealth Avenue after two explosions went off near the finish line of the 117th Annual Boston Marathon in Boston, Mass. on Monday, April 15, 2013. (Photo by Yoon S. Byun/The Boston Globe via Getty Images)
-
First responders transport an injured woman in a wheelchair where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders transport the wounded where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders rush to help injured people after two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
First responders rush to where two explosions occurred along the final stretch of the Boston Marathon on Boylston Street in Boston, Massachusetts, U.S., on Monday, April 15, 2013. Two powerful explosions rocked the finish line area of the Boston Marathon near Copley Square and police said many people were injured. Photographer: Kelvin Ma/Bloomberg via Getty Images
-
A Boston police officer clears Boylston Street following an explosion at the finish line of the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria at the finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
BOSTON - APRIL 15: (EDITOR'S NOTE: THIS IMAGE CONTAINS GRAPHIC CONTENT) A person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene on a stretcher. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: (EDITOR'S NOTE: THIS IMAGE CONTAINS GRAPHIC CONTENT) A person who was injured in an explosion near the finish line of the 117th Boston Marathon is taken away from the scene on a stretcher. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: A man lays on the ground after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: Emergency personnel respond to the scene after two explosions went off near the finish line of the 117th Boston Marathon on April 15, 2013. (Photo by David L. Ryan/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: A second explosion goes off (rear) as a runner was blown to the ground by the first explosion near the finish line of the 117th Boston Marathon. (Photo by John Tlumacki/The Boston Globe via Getty Images)
-
BOSTON - APRIL 15: A second explosion goes off (rear) as a runner was blown to the ground by the first explosion near the finish line of the 117th Boston Marathon. (Photo by John Tlumacki/The Boston Globe via Getty Images)
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. (AP Photo/Charles Krupa)
-
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. (AP Photo/Charles Krupa)
-
Medical workers wheel the injured across the finish line during the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
A flag flies over the finish line as medical workers aid injured people following an explosion at the finish line of the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria at the finish line, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/Charles Krupa)
-
BOSTON, MA - APRIL 15: State police guard an area near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images)
-
Boston to a T @Boston_to_a_T 1h
Second explosion going off @ Coply Square. #marathonmonday @universalhub pic.twitter.com/rOQ9EnTkx1
-
BOSTON, MA - APRIL 15: A member of the bomb squad investigates a suspicious item on the road near Kenmore Square after two bombs exploded during the 117th Boston Marathon on April 15, 2013 in Boston, Massachusetts. Two people are confirmed dead and at least 23 injured after two explosions went off near the finish line to the marathon. (Photo by Alex Trautwig/Getty Images)
-
This image from a Federal Bureau of Investigation and Department of Homeland Security joint bulletin issued to law enforcement and obtained by The Associated Press, shows the remains of a black backpack that the FBI says contained one of the bombs that exploded during the Boston Marathon. The FBI says it has evidence that indicates one of the bombs that exploded in the Boston Marathon was contained in a pressure cooker with nails and ball bearings, and it was hidden in a backpack. (FBI / AP)
-
Seattle Police Dept. vehicles block off a street in while remote controlled vehicles are used to examine a suspicious backpack in downtown Seattle, Tuesday, April 16, 2013. The backpack was found to be harmless, but in light of Monday's explosions at the Boston Marathon, authorities in Seattle and other cities increased security patrols and heightened the level of alertness for any possible threat to public safety. (Ted S. Warren / AP)
-
One of the blast sites on Boylston Street near the finish line of the 2013 Boston Marathon is seen in Boston, Tuesday, April 16, 2013, one day after bomb blasts killed three and injured over 140 people. FBI agents searched a suburban Boston apartment overnight and appealed to the public for amateur video and photos that might yield clues to who carried out the Boston Marathon bombing. (Elise Amendola / AP)
-
Investigators in white jumpsuits work the crime scene on Boylston Street following yesterday's bomb attack at the Boston Marathon April 16, 2013 in Boston, Massachusetts. Security is tight in the City of Boston following yesterday's two bomb explosions near the finish line of the Boston Marathon, that killed three people and wounding hundreds more. (Darren McCollester / Getty Images)