Hundreds of people gathered at a night-time vigil to remember the 27 people shot dead on Friday - including 20 primary school pupils - in one of the worst shootings America has seen.
The St Rose of Lima church in Newtown, Connecticut, was filled to capacity, with hundreds more outside, saying prayers and holding candles.
Suspected gunman Adam Lanza shot dead 18 children aged between five and 10 and six adults at Sandy Hook Elementary School, where his mother was a teacher, before killing himself. Two other children shot at the scene died in hospital later.
Lanza killed his mother Nancy at their home before he drove her car to the school and began the shootings shortly after the school day had started, a police source said. His girlfriend and another friend are still missing in New Jersey, the source added.
Connecticut police lieutenant Paul Vance said he and his colleagues had "never seen anything like it" in a press conference broadcast by Sky News, adding that it was "heart wrenching for us as well as for the families".Medical examiners were spending the night at the scene formally identifying the pupils and adults who were killed, state police said.
In New Jersey, Lanza's older brother Ryan, 24, of Hoboken, was being questioned by police but is not under arrest. He was co-operative during questioning and is not believed to have had any involvement in the attack, police added. He told investigators his brother, who lived with their mother in Connecticut, was believed to suffer from a personality disorder and be "somewhat autistic".
The shootings took place in one section of the school, in two rooms, according to Lt Vance. Speaking to journalists he said: "The shooter is deceased in the school, there's a great deal of work going on relative to that.
"That's the reason why we have not identified him as of yet. It is not a simplistic scene - we need to establish identity, we need to document the entire scene and we need to answer every single question surrounding exactly how and why this incident occurred."
Two pistols - a Glock and a Sig Sauer - were found inside the school, while a .223-calibre rifle was recovered from the back of a car at the site.
Connecticut governor Dan Malloy gave an official statement to the press on behalf of the state, saying that "evil visited this community today". Many of the victims were, he said, "beautiful, beautiful children, who had simply come to school to learn". He continued: "Their day ended a very different way than any of us could possibly have imagined. Quite frankly, as we stand here today, still can't imagine what transpired there."