At least 26 people, including 20 children, have reportedly been killed after a gunman opened fire at an elementary school in Newtown, Connecticut in one of the worst such attacks in US history.
Dozens of children, many holding hands and in tears, were rushed away from the school by their teachers and police.
A troubled 20-year-old loner with a history of autistic behavior is the monster behind a horrific shooting at a Connecticut elementary school that left 26 people, including 20 children.
Adam Lanza shot his mother Nancy, a kindergarten teacher, at the upscale suburban home they shared together and then took three of her guns and drove the Dandy Hook Elementary School about 9.30am.
He used two semi-automatic pistols, a Glock and Sig Sauer, and reportedly wiped out an entire classroom of young children and shot several in a second class before taking his own life.
Witnesses say he Lanza going from room-to-room shooting people after first killing the principal Dawn Hochsprung and psychologist execution-style after they confronted him in the hallway.
At least 100 rounds were fired during the attack, according to witnesses.
ABC News also reported that one group of students was still unaccounted for, quoting a source with a child in the school.
A White House spokesman said that President Barack Obama offered his sympathy "as a father" to the families.
Reports of a second gunman were unconfirmed. Another person was being held in police custody after he was detained in the woods near the school wearing camouflage pants.
"I was in the gym at the time ... we heard lots of bangs, and we thought that it was the custodian knocking stuff down. We heard screaming. And so went to the wall, and we sat down," a young boy told WCBS television.
"Then the police came in. It's like, is he in here? Then he ran out. Then somebody yelled get to a safe place, so we went to the closet in the gym and we sat there for a little while," he said, as stunned parents arrived.Then the police like were knocking on the door, and they're like, we're evacuating people, we're evacuating people. We ran out. They're police at every door leading us down this way, this way. Quick, quick, come on. We ran down to the firehouse. There's a man that pinned down to the ground with handcuffs on," he said.
Parents told the Hartford Courant that some students were still inside the school at 10.30 am, nearly an hour after the attack began.
SWAT teams were rushed to the school in the aftermath of the shooting, and a nearby hospital was also put on lockdown. Television images showed police and ambulances at the scene, and parents rushing toward the school.
Despite the tragedies support for tougher gun ownership laws is mixed, with many Americans opposing restrictions of what they consider to be a constitutional right to keep powerful firearms at home.