WASHINGTON -- Speaking before an auditorium of grieving parents, community members and others there to mourn the killing of 20 first graders and six adults from Newtown, Conn., President Barack Obama pledged Sunday to use the power of the office he occupies to end the epidemic of gun violence shaking the nation.

"We're not doing enough," the president said. "And we will have to change."

"We can't tolerate this anymore," he added. "These tragedies must end, and to end them, we must change. We will be told that the causes of such violence are complex, and it is true. No single law, no set of laws can eliminate evil from the world or prevent every senseless act of violence in our society. But that can't be an excuse for inaction. Surely we can do better than this."

The speech was the fourth and most direct that the president has given in the wake of a major instance of gun-related violence. His day had started with a trip to see his daughter, Sasha, at her dance rehearsal at the Music Center at Strathmore in North Bethesda, Md. And as he took the stage at Newtown High School, in a quiet New England town tucked in the southwestern corner of Connecticut, it was evident that he still occupied the mindset of a father frightened at vulnerability of young children.

"If there's even one step we can take to save one child, or one parent, or one town from the grief that has visited Tucson, and Aurora and Oak Creek and Newtown and communities from Columbine to Blacksburg before that, then surely we have an obligation to try," the president told the auditorium.

"In the coming weeks, I'll use whatever power this office holds to engage my fellow citizens, from law enforcement to mental health professionals to parents and educators in an effort to prevent more tragedies like this," he said. "Because what choice do we have?"

These moments have become disturbingly regular for this president. His speech in the aftermath of the Fort Hood shootings touched on the concept of justice for such heinous acts. His address to the victims of the Tucson, Ariz., shooting that nearly took former Rep. Gabrielle Gifford's (D-Ariz.) life focused on the need to renew the human spirit in the wake of seeming madness. His talk before the National Urban League convention following the shooting in Aurora, Colo., rested on the notion of community and how society can protect and better itself even amid epidemics of gun violence.

The address in Newtown offered a more stern call for cultural, or even legislative, change.

"We can't accept events like this as routine," he said. "Are we really prepared to say that we're powerless in the face of such carnage? That the politics are too hard? Are we prepared to say that the violence visited on our children year after year after year is somehow the price of our freedom?"

But like the three speeches before, the president stayed vague on the methods of seeing that change through. This could very well be out of a sense of proper setting. A vigil isn't always the best time to make policy points. But that may not be much comfort to those who are tired of the debate being ducked.

Obama's advocacy for gun control has, to this point, had an inverse relationship with his rise in elected politics. The state politician who once touted a comprehensive plan to get guns off the streets of Chicago was absent from the debates once he came to Washington. The Senate candidate who said it was a "scandal" that the assault weapons ban was allowed to lapse in 2004 became a president who pledged to pursue gun-control reform only within existing law.

Over time, caution was how the president became defined on the issue, his eloquent words of sympathy no longer sufficing.

"The president's tears were nice," said Toby Hoover, director of the Ohio Coalition Against Gun Violence, shortly after Obama addressed the Newtown shootings in a statement on Friday. Hoover lost her husband to gun violence when she was 30 years old, and was attending a candlelight vigil outside the White House gates. "But he was supposed to lead us. He told us that if we elected him, he'd give us hope. I need hope."

Whether the president's remarks on Sunday will change the viewpoints of Hoover or others -- or whether it will alter the contours of the gun control debate -- will be clearer in the weeks ahead. But certainly there is more room to operate.

Americans' support for stricter gun control laws appeared to grow in the days following the shooting at Sandy Hook Elementary School. According to a poll conducted by YouGov and The Huffington Post, 50 percent of respondents support stricter gun control laws, up from 43 percent in August.

This January, congressional Democrats plan to introduce identical bills in the House and Senate to renew the 1994 Federal Assault Weapons Ban, which was allowed to lapse in 2004 after 10 years. California Sen. Dianne Feinstein (D) said on Sunday that the bills would be introduced on the first day that Congress reconvenes next year.

Whether the ban would have changed the course of the Sandy Hook shootings is a complicated question. Authorities said Sunday that a Bushmaster .223 assault rifle was one of the weapons that 20-year-old Adam Lanza used to commit Friday's murders, and that it was purchased legally.

Connecticut has a statewide ban on certain types of assault weapons, but in the decade since the expiration of the federal assault weapons ban, gun manufacturers have devised numerous ways to get around state bans like the one in Connecticut by making small alterations.

Feinstein initially called for renewing the assault weapons ban in July, following the massacre of 12 people at a movie theater in Aurora, Colo. In the wake of this and other instances of gun violence, the White House has usually reaffirmed the president's support for the legislation, which President George W. Bush declined to renew when it expired. But that support is always accompanied by lines -- usually from the serving press secretary -- that the administration would work within existing law, rather than revisit old ones. Obama has actually loosened gun restrictions while in office and declined to pursue others that were recommended by his own Justice Department.

Feinstein and her caucus face a powerful and well-funded opposition to any legislation designed to curtail access to firearms.

Led by the National Rifle Association, pro-gun lobbying groups in Washington have donated more than $5 million to House and Senate candidates since the assault weapons ban expired in 2004. In 2012, the NRA's political action committee made more than $600,000 in federal campaign donations, overwhelmingly directed towards Republicans. The NRA has been largely silent in the wake of Friday's mass shooting, and an NRA spokeswoman said that the group would not release any comments "until the facts are thoroughly known."

In the meantime, the pro-gun lobby faced an ongoing barrage of criticism on Sunday from a wide range of public figures. As Feinstein was calling on Congress to act on gun control, across town, the dean of the Washington National Cathedral, the Very Rev. Gary Hall called on people of faith to "serve as a counterweight to the gun lobby," and "stand together with our leaders and support them as they act to take assault weapons off the streets."

View the full speech at the top of the story, and see excerpts below:

CORRECTION: A previous version of this story stated incorrectly the type of weapon Adam Lanza reportedly used during the attack in Newtown, Conn. It was a Bushmaster .223 assault rifle.

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  • Barack Obama

    President Barack Obama arrives at the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Barack Obama

    President Barack Obama greets Gov. Dannel Malloy during his arrival at the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/The Hartford Courant, Stephen Dunn, Pool)

  • Barack Obama

    President Barack Obama pauses during a speech at an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • Barack Obama

    President Barack Obama walks off after delivering a speech at an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Barack Obama

    President Barack Obama speaks during an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • Barack Obama

    President Barack Obama greets State Senate Minority Leader John McKinney, R-Fairfield, on his arrival, before the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting inside the Newtown High School auditorium in Newtown, Conn., Sunday night, Dec. 16, 2012. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. (AP Photo/The Hartford Courant, Stephen Dunn, Pool)

  • Barack Obama

    President Barack Obama pauses as he delivers a speech during an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Barack Obama

    President Barack Obama speaks during an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/The Hartford Courant, Stephen Dunn, Pool)

  • Barack Obama

    President Barack Obama pauses as he delivers a speech at an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Barack Obama

    Residents pray during an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • Barack Obama

    President Barack Obama pauses as he delivers a speech at an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • Barack Obama

    President Barack Obama pauses as he delivers a speech at an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School on Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • US-SCHOOL-SHOOTING-MEMORIAL

    US President Barack Obama makes his way off the stage after speaking at a memorial service for the victims and relatives of the Sandy Hook Elementary School shooting on December 16, 2012 at the Newtown High SChool in Newtown, Connecticut. Twenty-six people were killed when a gunman entered Sandy Hook Elementary and began a shooting spree. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Barack Obama

    President Barack Obama walks off stage after delivering a speech at an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School on Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Barack Obama

    President Barack Obama pauses as he delivers a speech during an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the elementary school on Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • US-SCHOOL-SHOOTING-MEMORIAL

    US President Barack Obama pauses as he speaks during a memorial service for the victims and relatives of the Sandy Hook Elementary School shooting on December 16, 2012 in Newtown, Connecticut. Twenty-six people were killed when a gunman entered Sandy Hook Elementary and began a shooting spree. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

  • Barack Obama

    President Barack Obama returns to the White House in Washington after attending an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School on Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jacquelyn Martin)

  • Barack Obama

    Residents greet each other before the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Barack Obama

    Air Force One carrying President Barack Obama is seen leaving Bradley Air National Guard Base in East Granby, Conn., Sunday, Dec. 16, 2012. The president was in Connecticut to attend a memorial for the victims of the Sandy Hook Elementary School shooting where 26 people, including 20 children, were killed Friday. (AP Photo/Jessica Hill)

  • Julie LaPak, right, and Scott Emslie, of Newton, Conn., watch President Obama delver his speech at the Iron Bridge restaurant, Sunday, Dec. 16, 2012 in Newtown, Conn. (AP Photo/Mary Altaffer)

  • A mourner looks on during an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Surendra Khera, left, Manjaree Daw, center and Indira Khera, of Simsbury, Conn., watch President Obama deliver his speech at the Iron Bridge restaurant, Sunday, Dec. 16, 2012 in Newtown, Conn. The president spoke during an interfaith vigil for the victims of the Sandy Hook Elementary School shooting. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Mary Altaffer)

  • Barack Obama

    Residents look on as President Barack Obama delivers remarks at an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • A mourner weeps while listening to President Barack Obama speak on a loudspeaker while sitting outside a memorial at Newtown High School for the victims of the Sandy Hook Elementary School shooting, Sunday, Dec. 16, 2012, in Newtown, Conn. (AP Photo/David Goldman)

  • C.J. Singh, center, and other members of the Sikh community hold a candlelight vigil outside Newtown High School before an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • Residents hold a candlelight vigil outside Newtown High School after President Barack Obama delivered remarks at an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • A young boy places a candle with others at the base of a flagpole outside Newtown High School before an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • Eknoor Kaur, 3, stands with her father Guramril Singh during a candlelight vigil outside Newtown High School before an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • Members of the Sikh community hold a candlelight vigil outside Newtown High School before an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • U.S. Sen. Joseph Lieberman, I-Conn., top right, Rep. Rosa DeLauro, D-Conn., left, Sen-elect Chris Murphy, center, and Lt. Gov. Nancy Wyman, right, wait for the arrival of President Barack Obama before the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting inside the Newtown High School auditorium in Newtown, Conn., Sunday night, Dec. 16, 2012. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. (AP Photo/The Hartford Courant, Stephen Dunn, Pool)

  • Residents look on during an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. President Barack Obama is schedule to speak during the vigil. (AP Photo/ Evan Vucci)

  • Barack Obama

    Residents greet each other before the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. President Barack Obama is scheduled to speak during the vigil. (AP Photo/ Evan Vucci)

  • Barack Obama

    Residents greet each other before the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the school Friday and opened fire, killing 26 people, including 20 children. President Barack Obama is to scheduled to speak at the event. (AP Photo/ Evan Vucci)

  • Residents look on during an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. President Barack Obama is scheduled to speak during the vigil. (AP Photo/Evan Vucci)

  • Barack Obama

    Residents greet each other before the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • People wait in line to attend an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • Barack Obama

    Residents greet each other before the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • People arrive at Newtown High School to attend an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown on Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • Residents greet each other before the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Kayla Hopson and her daughter Lilliana, 9, left, and Janine Caswell and her daughter Genesis, 8, stand wrapped in Red Cross blankets to protect themselves from the cold, rainy weather as they wait in line to attend an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • Residents wait for the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Eight-year old Shayne Frate, a third grade student at Sandy Hook Elementary School, hangs from her mother Valerie's back, wrapped in a Red Cross blanket to protect her from the cold, rainy weather, as she waits in line to attend an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • People wait in line to attend an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown on Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • Residents wait for the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Red Cross volunteer Michael Cianciolo distributes blankets to protect people from the cold, rainy weather as they wait in line to attend an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • Red Cross personnel provide blankets, water, snacks and even stuffed toys to keep people comfortable as they wait in line to attend an interfaith vigil with President Barack Obama, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Jason DeCrow)

  • Residents wait for the start of an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/Evan Vucci)

  • Barack Obama

    Residents greet each other before an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012 at Newtown High School in Newtown, Conn. A gunman walked into Sandy Hook Elementary School Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • Barack Obama

    Residents greet each other before an interfaith vigil for the victims of the Sandy Hook Elementary School shooting on Sunday, Dec. 16, 2012, at Newtown High School in Newtown, Conn. A gunman walked into the elementary school Friday and opened fire, killing 26 people, including 20 children. (AP Photo/ Evan Vucci)

  • A U.S. flag flies at half staff outside the Newtown High School before President Barack Obama is scheduled to attend a memorial for the victims of the Sandy Hook Elementary School shooting, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/David Goldman)

  • People wait in line to enter Newtown High School for a memorial vigil attended by President Barack Obama for the victims of the Sandy Hook Elementary School shooting, Sunday, Dec. 16, 2012, in Newtown, Conn. A gunman walked into Sandy Hook Elementary School in Newtown Friday and opened fire, killing 26 people, including 20 children. (AP Photo/David Goldman)