A headteacher and a school psychologist went to the aid of their students after hearing gunshots at a Connecticut school, according to reports.
Dawn Hochsprung and therapist Diane Day were in a meeting at Sandy Hook Elementary School in Newtown on Friday morning when the gunman, thought to be the son of a teacher at the school, began shooting at around 9.30am.
The pair leaped out of their seats after hearing gunshots and ran to see what was going on, according to Ms Day.
She told the Wall Street Journal: "We were there for about five minutes chatting, and we heard Pop! Pop! Pop!
"I went under the table. They didn't think twice about confronting or seeing what was going on."
Ms Hochsprung is believed to have switched on a loudspeaker system in the school to alert students and staff to the danger.
A woman comforts a girl at a vigil to the shooting victims on Friday nightFourth-grade teacher Theodore Varga said: "You could hear the hysteria that was going on.
"Whoever did that saved a lot of people. Everyone in the school was listening to the terror that was transpiring."
He added that a school caretaker also ran out warning people there was a gunman on the premises.
Ms Hochsprung was confirmed to be among seven adults and 20 children killed during the rampage. The school psychologist was also reported to have been killed.
The masked gunman - reportedly armed with a Glock and a Sig Sauer handguns as well as a .223-calibre rifle - has been named as 20-year-old Adam Lanza.
Robert Licata, whose six-year-old son was in one of the classrooms when the gunman burst in and opened fire, said he told him the shooter did not say anything.
He said: "That's when my son grabbed a bunch of his friends and ran out the door.
"He was very brave. He waited for his friends."
First-grade teacher Kaitlin Roig barricaded her 15 students inside a tiny bathroom with a bookshelf and told them to be "absolutely quiet".
She told ABC News: "I said, 'there are bad guys out there now. We need to wait for the good guys'.
"They asked, 'Can we go see if anyone is out there? I just want Christmas. I don't want to die, I just want to have Christmas.'"