WASHINGTON (AP) — President Barack Obama is vowing to use "whatever power this office holds" to safeguard the nation's children, raising the prospect that he will pursue policy changes to stem gun violence in the wake of an elementary school massacre.

"Because what choice do we have?" a somber Obama said at a Sunday evening vigil in the grieving community of Newtown, Conn. "We can't accept events like this as routine. Are we really prepared to say that we're powerless in the face of such carnage? That the politics are too hard?"

The newly re-elected president offered few specifics about how he planned to proceed, saying only that he will engage with law enforcement, mental health professionals, parents and educators in the coming weeks. Just days after the shooting at an elementary school, Obama is already facing pressure from fellow Democrats and New York City Mayor Michael Bloomberg to tackle gun control legislation, a contentious issue he avoided as he sought a second term.

But Friday's shooting, which left 20 children and eight adults dead, appears to have spurred some soul-searching by Obama, who told Connecticut's governor that Friday was the most difficult day of his presidency. Speaking to families of the victims and first responders, Obama said Sunday that he had been reflecting on whether the country was doing enough to give its children "the chance they deserve to live out their lives in happiness and with purpose."

"And if we're honest with ourselves, the answer is no. We're not doing enough, and we will have to change," Obama said.

Sunday marked the fourth time in Obama's presidency that he has traveled to a community shaken by a mass shooting. Just this summer, he made a similar visit to Aurora, Colo., where a dozen people were killed in a movie theater attack.

Drawing on his past experiences, Obama said he was mindful that mere words would not be enough to heal the depths of Newtown's sorrow.

"I can only hope that it helps for you to know that you are not alone in your grief," Obama said during the vigil, which followed his private meeting with families of the victims.

The president closed his remarks by reading the first names of the kids, slowly, in the most wrenching moment of the night. Cries and sobs filled the room.

Said Obama of the girls and boys who died: "God has called them all home. For those of us who remain, let us find the strength to carry on and make our country worthy of their memory."

Inside the room, children held stuffed teddy bears and dogs. The smallest kids sat on their parents' laps.

There were tears and hugs, but also smiles and squeezed arms. Mixed with disbelief was a sense of a community reacquainting itself all at once.

One man said it was less mournful, more familial. Some kids chatted easily with their friends. The adults embraced each other in support.

"We're halfway between grief and hope," said Curt Brantl, whose daughter was in the library of the elementary school when the shootings occurred. She was not harmed.

Police and firefighters got hugs and standing ovations when they entered. So did Obama.

"We needed this," said the Rev. Matt Crebbin, senior minister of the Newtown Congregational Church. "We needed to be together to show that we are together and united."

The shootings have restarted a debate in Washington about what politicians can to do help — gun control or otherwise. Obama has called for "meaningful action" to prevent killings.

Sen. Dianne Feinstein, D-Calif., said Sunday she will introduce legislation next year to ban new assault weapons, as well as big clips, drums and strips of more than 10 bullets.

Police say the gunman, Adam Lanza, was carrying an arsenal of ammunition big enough to kill just about every student in the school if given enough time. He massacred 20 students and six teachers and administrators before shooting himself in the head just as he heard police drawing near, authorities said.

A Connecticut official said the gunman's mother was found dead in her pajamas in bed, shot four times in the head with a.22-caliber rifle. The killer then went to the school with guns he took from his mother and began blasting his way through the building.

"There is no blame to be laid on us but there is a great burden and a great challenge that we emerge whole," First Select Woman Patricia Llodra said. "It is a defining moment for our town, but it does not define us."

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AP White House Correspondent Ben Feller contributed to this report.