"I was in the gym and I heard a loud, like seven loud booms, and the gym teachers told us to go in the corner, so we all huddled," one student told NBC Connecticut during its live broadcast. "And I kept hearing these booming noises. And we all... started crying".
"All the gym teachers told us to go into the office where no one could find us," she added. "So then a police officer came in and told us to run outside. So we did and we came in the firehouse and waited for our parents."
Pictures showed panicked children, some of them crying, being led out to safety by their teachers.
US President Barack Obama was briefed by his top counter-terrorism advisor on the deadly shooting shortly after which he called the FBI Director and the Connecticut Governor.
Image: Parents leave a staging area after being reunited with their children following a shooting at the Sandy Hook Elementary School in Newtown, Conn., about 60 miles (96 kilometers) northeast of New York City, Friday, Dec. 14, 2012. An official with knowledge of Friday's shooting said 27 people were dead, including 18 children. It was the worst school shooting in the country's history. (AP Photo/Jessica Hill)