​Sandy Hook survivors: "We're at a tipping point" on gun laws

The heroic teachers of Sandy Hook Elementary ... 09:08

It's been nearly two years since a disturbed young man, Adam Lanza, opened fire at the Sandy Hook Elementary School in Newtown, Conn., killing 20 young children and six adults. Some of the teachers are beginning to tell stories of what they heard and saw that day -- and trying to make certain what happened in Newtown can't happen elsewhere. Our Cover Story this morning is reported by Jane Pauley:

"Something like this rips you to your core, and we came back to school ripped to shreds," said Abbey Clements, a 2nd grade teacher. "But we came back to do the best we could with these kids who we loved and we got lucky enough to survive with."

She was one of four women working at Sandy Hook Elementary School on December 14, 2012.

All four and all of the children in their care got out of the building safely.

All four only now are speaking out about the impact of that terrible day.

"Nobody cowered under a chair," said Clements. "Everybody took care of those kids the best that we knew how to in the insanity that was unfolding before us."

Reading specialist Becky Virgalla was in a meeting in a conference room near the school's front door. "We heard this loud noise and I thought the roof was collapsing," she said. "I just looked at someone and said, 'What was that?'"

A 20-year-old gunman had blasted through the glass entryway with a semi-automatic rifle.

"Three people got up and ran out into the hall. We were ready to follow them out to go investigate the sound. I was three steps away from going out into the hall when my principal, Dawn Hochsprung, shouted back, 'Shooter! Stay put!'"

Someone had called 911 on a phone linked to the school intercom, which in the chaos was accidentally turned on. The ensuing gunfire could be heard in classrooms all over the school.

"The speaker, I just wanted to climb up on the table underneath it and rip it down," said Clements, "but I was scared 'cause we were always told to stay low, and I had no idea where the shots were coming from. So I tried to sing songs, and we tried to read, and many of us did similar things."

The shooter went into two first-grade classrooms. Carol Wexler's second-grade classroom was directly across the hall. For her, there was no turning off the sounds only feet away.

"I haven't told this story," Wexler said. "I think this is a very difficult conversation to have just because of what it brings up for me."

Five minutes: That's how long it took the gunman to fire 154 shots -- the last, to take his own life.

"When I gave my report to the police I said, 'Oh, half-hour, 45 minutes," said Virgalla. "It seemed to go on forever. I heard every one of those 154 shots. It just went on forever."