Police are investigating reports that 20-year-old Adam Lanza was involved in an "altercation" at the school less than 24 hours before the massacre, described as the worst mass school killing in US history.
Lanza, said to be a loner who may have suffered from a personality disorder, is thought to have argued with four teachers at the school, three of whom died in the shooting. The fourth, who was not on duty, is now being spoken to by investigators.
Lanza forced his way into the school on Friday morning and fired more than 100 shots, killing 26 people in two classrooms.
The killer, who wore black military-style fatigues and body armour, later turned the gun on himself. He had earlier shot and killed his mother, Nancy, at the home they shared nearby.
Further chilling details of the horrifying events within the school emerged last night as survivors began to speak of the tragedy.
Headteacher Dawn Hochsprung, 47, and school psychologist Mary Sherlach, 56 were hailed heroes after they died confronting the killer when he first entered the school.
Tributes were also paid to young teacher Victoria Soto, 27, who was found huddled over the bodies of her pupils. It is thought she tried to shield them from gunfire when Lanza started shooting in her classroom.
Three other teachers, who have not yet been identified, were also murdered. One survivor, teacher Kaitlin Roig, spoke of how she tried to comfort children as Lanza stalked through the school. "I told them we had to be absolutely quiet, because I was just so afraid if he did come in, then he would hear us and just start shooting the door," she said.
"I said to them, 'I need you to know that I love you all very much and that it's going to be okay', because I thought that was the last thing they were ever going to hear."
Music teacher Maryrose Kristopik also spoke of trying to comfort her terrified class. She said she took the children into a closet and "talked with them to keep them quiet. I told them that I loved them. I said there was a bad person in the school. I didn't want to tell them anything past that.
"I was just trying to be as strong as possible ... Of course, I was afraid too"
MaryAnne Jacobs, assistant librarian at the school, told today how she hid with 18 first grade children in a storage cupboard.
She said she followed the usual drill for emergency procedures, telling the children to be quiet and sit down before taking them initially to a place they thought safe and then to the room normally used to house servers for the library computers.