"The majority of those who died today were children. Beautiful little kids between the ages of 5 and 10 years old," he said.

The bodies of the young victims remained where they fell Friday night, as authorities worked to positively identify them.

Flags were ordered to fly at half-staff nationwide in tribute to the victims, and candlelight vigils were planned across the country as Americans came together to try to comprehend the tragedy.

At a vigil in Newtown, just a mile away from the school, mourners spilled from St. Rose of Lima Roman Catholic Church, which was filled to capacity.

"This is most definitely the worst thing we've experienced in town," Newtown Police Lt. George Sinko said.

Parents, meanwhile, struggled to come up with answers for their children who were among those safely evacuated Friday.

Aimee Seaver's daughter is a first-grader at Sandy Hook.

"It's a very rough night here," she told "AC 360." "When your first-grader goes to bed and says, 'Mommy, is anyone from my class last year -- are they all OK?' and you look at them and say, 'I'm not really sure,' it's a rough night to tell that to your 7-year-old."

It is not yet known how the gunman entered the school.

Hochsprung, the slain principal, had recently installed a new security system to ensure student safety.

Under the new system, every visitor was required to ring a doorbell at the front entrance after the doors locked at 9:30 a.m. and report to the main office to sign in.

Police began receiving reports of shots fired around 9:40 a.m. Friday.

In 1999, at Columbine High School in Littleton, Colorado, two students shot 13 people to death before killing themselves.