NEWTOWN, Conn. - The gunman in the Connecticut shooting rampage was carrying an arsenal of hundreds of rounds of especially deadly ammunition - enough to kill just about every student in the school if given enough time, authorities said Sunday, raising the chilling possibility that the bloodbath could have been far worse.
Adam Lanza shot himself in the head just as he heard police drawing near to the classroom where he was slaughtering helpless children, but he had more ammunition at the ready in the form of multiple, high-capacity clips each capable of holding 30 bullets.
The disclosure on Sunday sent shudders throughout this picturesque New England community as grieving families sought to comfort each other during church services.
Hours later, President Barack Obama told mourners at a vigil that the nation is failing to keep its children safe.
He spoke for a nation in sorrow, but the slaughter of all those little boys and girls left Obama, like so many others, reaching for words. Alone on a spare stage after the worst single day of his presidency, the commander in chief was a parent in grief.
"I am very mindful that mere words cannot match the depth of your sorrow, nor can they heal your wounded hearts," Obama said at an evening vigil in the grieving community of Newtown, Conn. "I can only hope that it helps for you to know that you are not alone in your grief."
He pledged to seek change in memory of the 26 teachers and schoolchildren who were killed in the second-deadliest school shooting in U.S. history.
"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?"
Obama continued, "Can say that we're truly doing enough to give all the children of this country the chance they deserve to live out their lives in happiness and with purpose? I've been reflecting on this the last few days," Obama said, somber and steady as some in the audience wept.
"If we're honest without ourselves, the answer is no. And we will have to change."
With so much grieving left to do, many of Newtown's 27,000 people wondered whether life could ever return to normal. And as the workweek was set to begin, parents weighed whether to send their own children back to school.
Gov. Dannel Malloy said the shooter decided to kill himself when he heard police closing in about 10 minutes into the attack.
"We surmise that it was during the second classroom episode that he heard responders coming and apparently at that decided to take his own life," Malloy said on ABC's "This Week."
Police said they found hundreds of unused bullets at the school, which enrolled about 450 students in kindergarten through fourth grade.
"There was a lot of ammo, a lot of clips," said state police Lt. Paul Vance. "Certainly a lot of lives were potentially saved."
The chief medical examiner has said the ammunition was designed to expend its energy in the victim's tissues and stay inside the body to inflict the maximum amount of damage.
The sorrowful interfaith service was stark and spare, with a stage that held only a small table covered with a black cloth, candles and the presidential podium.
Privately, Obama told the governor that Friday was the most difficult day of his presidency.
Also Sunday, 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, got inside by breaking a window and began blasting his way through the building.
Federal agents have concluded that Lanza visited an area shooting range, but they do not know whether he actually practiced shooting there.
Agents also determined that Lanza's mother visited shooting ranges several times, but it's still not clear whether she brought her son to the range or whether he ever fired a weapon there.
Investigators have offered no motive for the shooting, and police have found no letters or diaries that could shed light on it.