A mournful President Obama said during his visit to Newtown, Conn., on Sunday that the nation is failing to keep its children safe, pledging that change must come after an elementary-school massacre left 20 children dead.

"What choice do we have?" Obama said. "Are we really prepared to say that we're powerless in the face of such carnage, that the politics are too hard?"

In a vigil for the fallen, in a moment of grief that spread around the world, Obama conceded that none of his words would match the sorrow. But he declared to the community of Newtown: "You are not alone."

In other news from Newtown on Sunday:

* Connecticut's chief medical examiner, Dr. H. Wayne Carver II, said that Lanza shot his mother, Nancy Lanza, four times in the head. She was found dead in her pajamas in bed. Carver said Adam Lanza died of a self-inflicted gunshot wound to the head.

* Connecticut Gov. Dannel Malloy said Lanza shot himself when he heard police coming. Authorities said he had hundreds of rounds of ammunition left to carry out significant carnage.

"There was a lot of ammo, a lot of clips," said State Police Lt. Paul Vance. "Certainly a lot of lives were potentially saved."

* Nancy Lanza told a drinking buddy less than a week before the Newtown rampage that Adam "was getting worse," the New York Daily News reported. The anonymous pal said that Nancy told him that Adam had burned himself with a lighter. "It was like he was trying to feel something," Nancy Lanza told the man.

* Newtown officials couldn't say whether Sandy Hook Elementary School would ever reopen.

School officials were discussing how to send survivors back to class, but Newtown police Lt. George Sinko said he "would find it very difficult" for students to return to the school. But, he added: "We want to keep these kids together. They need to support each other."

Jim Agostine, superintendent of schools in nearby Monroe, said plans were being made for students from Sandy Hook to attend classes in his town this week.