BOSTON — Boston Police Commissioner Edward Davis, who led his department's response to the Boston Marathon bombing, is stepping down, a department spokeswoman said Sunday.

Davis gave his resignation to Mayor Thomas Menino and will hold a news conference Monday to discuss his future plans, police spokeswoman Cheryl Fiandaca said.

The decision by Davis to step down is perhaps not surprising. Boston is poised to have a new mayor for the first time in two decades after Menino opted not to seek another term.

A statement from Menino's office thanked Davis for his "tremendous work over the past seven years" and promised to work with Davis to ensure a smooth transition when new mayor finds a permanent successor.

Davis was thrust into the national spotlight on April 15 when twin explosions near the marathon finish line killed three people and wounded more than 260.

Along with Menino and Gov. Deval Patrick, Davis ordered a daylong, city-wide lockdown after the two bombing suspects were involved in a shootout with police.

Once suspect died following the gun battle, a second was later taken into custody and is awaiting trial.

Delivering the commencement address at the University of Massachusetts Lowell a month later, Davis said the bombing taught him much about police work – and the resiliency of human beings.

"I learned to think the unthinkable," Davis said. "I learned that the most horrific of circumstances can produce the most inspirational and heroic of actions, not just by one single person, but by hundreds of them."

Davis, 57, was appointed Boston's top cop by Menino in 2006. He previously served as the Lowell, Mass., superintendent of police.

Davis' departure comes just as the race to replace Menino kicks into high gear. A preliminary election on Tuesday will whittle a dozen candidates down to two for the Nov. 5 election.

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  • Gov. Deval Patrick (D-Mass.)

    “This is a horrific day in Boston. My thoughts and prayers are with those who have been injured. I have been in touch with the President, Mayor Menino and our public safety leaders. Our focus is on making sure that the area around Copley Square is safe and secured. I am asking everyone to stay away from Copley Square and let the first responders do their jobs.”

  • President Barack Obama

    <blockquote>The American people will say a prayer for Boston tonight. And Michelle and I send our deepest thoughts and prayers to the families of the victims in the wake of this senseless loss. ... We still do not know who did this or why. And people shouldn’t jump to conclusions before we have all the facts. But make no mistake -- we will get to the bottom of this. And we will find out who did this; we'll find out why they did this. Any responsible individuals, any responsible groups will feel the full weight of justice. Today is a holiday in Massachusetts -- Patriots’ Day. It’s a day that celebrates the free and fiercely independent spirit that this great American city of Boston has reflected from the earliest days of our nation. And it’s a day that draws the world to Boston’s streets in a spirit of friendly competition. Boston is a tough and resilient town. So are its people. I'm supremely confident that Bostonians will pull together, take care of each other, and move forward as one proud city. And as they do, the American people will be with them every single step of the way.</blockquote>

  • Vice President Joe Biden

    VP Biden: "Our prayers are with those people in Boston who have suffered injuries. I don’t know how many there are."

  • Sen. William "Mo" Cowan (D-Mass.)

  • Sen. Elizabeth Warren (D-Mass.)

  • Former Mass. Gov. Mitt Romney (R)

  • Former Sen. Scott Brown (R-Mass.)

  • House Majority Leader Eric Cantor (R-Va.)

  • Rep. John Tierney (D-Mass.)

  • Rep. Joe Kennedy III (D-Mass.)

  • Rep. Niki Tsongas (D-Mass.)

  • Rep. Ed Markey (D-Mass.)

  • Rep. Debbie Wasserman Schultz (D-Fla.)

  • Senator John McCain (R-Ariz.)

  • New Jersey Gov. Chris Christie (R)

  • Oklahoma Gov. Mary Fallin (R)

  • Gov. Maggie Hassan (D)

  • Rep. Chris Murphy (D-Conn.)

  • Speaker John Boehner

  • Senate Minority Leader Mitch McConnell (R-Ky.)

  • Sen. Chris Coons (D-Del.)

  • Sen. Jeff Flake (R-Ariz.)

  • Sen. Mike Crapo (R-Idaho)

  • Sen. Tim Scott (R-S.C.)

  • Sen. Kelly Ayotte (R-N.H.)

  • Sen. Ted Cruz (R-Texas)

  • Sen. John Cornyn (R-Texas)

  • Sen. Dean Heller (R-Nev.)

  • Sen. Mike Lee (R-Utah)

  • Sen. Tom Carper (D-Del.)

  • Sen. Saxby Chambliss (R-Ga.)

  • Sen. Jeanne Shaheen (D-N.H.)

  • Sen. Roy Blunt (R-Mo.)

  • Sen. Dan Coats (R-Ind.)

  • Sen. Pat Toomey (R-Pa.)

  • Sen. Angus King (I-Maine)

  • Sen. Debbie Stabenow (D-Mich.)

  • Sen. Mazie Hirono (D-Hawaii)

  • Sen. Pat Roberts (R-Kan.)

  • Sen. Johnny Isakson (R-Ga.)

  • Sen. Mark Begich (D-Alaska)

  • Sen. Heidi Heitkamp (D-N.D.)

  • Sen. Chuck Schumer (D-N.Y.)

  • Sen. Richard Blumenthal (D-Conn.)

  • Sen. Jerry Moran (R-Kan.)

  • Sen. David Vitter (R-La.)

  • Sen. Ben Cardin (D-Md.)

  • Sen. Brian Schatz (D-Hawaii)

  • Sen. Susan Collins (R-Maine)

  • Sen. Joe Donnelly (D-Ind.)

  • Sen. Deb Fischer (R-Neb.)