Nancy was a gun collector and showed off a rifle she'd recently purchased to Newtown resident Dan Holmes.

She told Holmes she'd go target shooting with her boys pretty often.

On Friday, Lanza took one of his mother's guns and killed her at their house.

He put on black fatigues and a military vest. He grabbed three guns from the house -- a semi-automatic AR-15 assault rifle made by Bushmaster and pistols made by Glock and Sig Saeur -- and made his way to the school.

'Pop, pop, pop'

Everyone at Sandy Hook felt safe in the school building on Dickinson Drive.

Earlier this year, Hochsprung had a new security system installed. It required all the school doors to be locked by 9:30 and visitors to be visibly identified before being buzzed in.

School started Friday with announcements on the PA system. Hochsprung was in a meeting with the vice principal, and the school's psychologist, Mary Sherlach, was in a room near the entrance.

The mother of a struggling second grader had come in to discuss her child. That's when Lanza blasted his way inside.

The mother in the meeting heard a "pop, pop, pop." The sound was coming from the hall. She ducked under the table. She cowered.

She must have heard at least 100 rounds, she said. "Just shooting and shooting and shooting."

She dialed 911.

Hochsprung, Sherlach and the vice principal stepped out to see what was going on. The vice principal was wounded in the foot. She was the only one of the three who came back into the room.

Systematic carnage

The school's PA system was still on from the morning announcements and every sound in the building was amplified.

Every pop, every bang, every boom was that much louder and clearer.

When she heard the crackling over the PA, school library clerk Mary Ann Jacob called the office to tell them the system was still on. The office staffer told her there was a shooter in the building.

She had practiced lockdown drills many times with the kids. They knew they were supposed to go a spot between bookcases against a wall. They couldn't be seen from the windows there.

But then Jacob realized one of the doors in the room wasn't locked. So she hustled the 6-year-olds under her watch into a back storage room and locked them in there. She handed out pieces of paper and crayons to keep them quiet.

When Lanza began shooting, some of the students thought the noise was the clanging of pots and pans. One teacher thought it was folding chairs brought in for a concert falling to the ground like dominoes.

Fourth-grader Brendan Murray was inside the school's gym. He thought the custodian was knocking things down.

First-grader Aiden Licata, whose class was going to make the gingerbread house, thought it was the sound of hammers.

Aiden's teacher, Victoria Soto, and other school employees scrambled to get the students into safe areas of the building.

Janet Vollmer closed her classroom doors, locked and covered the windows and began reading a story to her kindergarteners to keep them calm. But they all knew something was terribly wrong.

"We're going to be safe," Vollmer told them, "because we're sitting over here and we're all together."