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This is a rush transcript from "On the Record," December 18, 2012. This copy may not be in its final form and may be updated.
SHARI BURTON, SANDY HOOK ELEMENTARY TEACHER'S AIDE: ... [I heard him] shoot his way into the building. He shot out the glass.
VAN SUSTEREN: That is Shari Burton, a Sandy Hook teacher's assistant, who called 911 just moments after hearing those first horrifying shots. Tonight, she tells our Griff Jenkins how she kept 16 students safe as gunman Adam Lanza began his cruel killing spree.
BURTON: I called 911, and they said that they had some calls come through already, and they asked me to describe what I was hearing. And at that time, all I was hearing was, Pop, pop, pop, pop, pop, pop. And it wasn't stopping. And he said, Do you think it's gunshots? And I said, I think it's gunshots.
At that time, I did not realize that our teacher could not lock our door, but she had saw the custodian. She said, Our door won't lock, and he shooed her into our room and she closed the door. And he came back. He stayed in the hallway and he locked our doors.
So now our doors are locked and I'm sitting on the floor. I'm as close as I can be, and our students are huddled, and the shooting wasn't stopping.
The loudspeaker tripped, and I thought I heard Barbara Halstead, our secretary. And I believe what I heard was, Oh, my God, and some crying. And then the phone went down, but the loudspeaker was still on, and I could hear the shooting from the door, but I could hear it through the loudspeaker. It was -- you could hear both. Like, I don't know where I (ph) was, and it didn't sound like it was coming our direction, but it was going on and on.
I was on the phone with 911, and my phone beeped and a text came in, and my immediate reaction was, Oh, my God, it's my children. They are first responders with the Sandy Hook Volunteer Fire and Rescue, and I knew they were worried. And so the 911 caller said -- he said, I'm going to put you on hold for a minute, ma'am. There's lots of calls coming in. As long as you're safe -- and again, they asked me how many people were in the room. And I said there's 16 children and two adults, and we are safe now.
And I said, When is someone coming? Is someone coming soon? And he put me on hold. When he put me on hold, I hung up because I wanted to text my children. My text -- my phones were going off. My son was in lockdown at the high school. My daughter was a first responder.
She actually hadn't gotten the call yet. She wanted to know why I didn't leave her the car. I mean, she's home from college. And so I said, Lockdown, shooter in school, I'm OK. That's all I could manage to type. And then I texted my son, I'm OK.
I don't know, it seemed like it went on for a really long time. I called 911 back and I got a woman this time, and I asked when was help coming. The shooting was still going on. I heard the shooting stop briefly and then start again.
GRIFF JENKINS, FOX NEWS CORRESPONDENT: How long -- how long of a period of shooting do you think you heard?
BURTON: Twenty minutes, twenty-five minutes? You know, it seemed forever.
JENKINS: What did it sound like? You said it stopped for a moment?
BURTON: It was eerily quiet. You know, you would hear nothing, and then you heard the pop, pop, pop, pop. I mean, it just -- and it's -- you know, all I could think of was of my co-workers and my friends and children. I didn't know.
At one point, someone shook our door, but they didn't say anything, so I don't know who it was. I don't believe the shooter was ever in our side of the building.
I know that our custodian had stayed in our hallway out the entire time. And when the police stormed or came in, I heard the conflict -- you know, he was trying to explain to them that he was the custodian, and I could hear that. I could hear the yelling between the two of them. You know, the police are coming in.
And the first time the police shook our door and said, Police, open up, I looked at my co-teacher, my -- my -- my teacher, you know, my supervisor, and I shook my head because it was one person, you know? I didn't think we should open the door. And then moments later, I could hear several police officers. And I could hear the next classroom, and I could hear some crying and I could hear them being led out.
So then I looked at my teacher, and she opened the door and the police officers were there. And we -- they lined the hallways, and all we saw was them looking at us. And we held our children's hands and we raced through the back of the building. They led us out the back and we went to the firehouse.
JENKINS: Rick, the custodian, was essentially just standing guard for your classroom.
BURTON: I believe so. Yes. I believe him and Barbara Halstead played a huge part in saving many of the lives.
JENKINS: Barbara is the secretary...
BURTON: She is.
JENKINS: ... who was on the intercom.
BURTON: Yes. I believe. I don't know for sure. Like...
BURTON: But I believe I heard her trip the intercom.
JENKINS: And you thought perhaps she had not survived.
BURTON: And I thought -- yes. Yes. Yes.
JENKINS: But you later found out...
BURTON: ... that she was OK. Whenever they said -- because her daughters are my friends, and so when I saw her daughter, who was a first responder, I thought that her mom had died. And I didn't know what to say to her, and she said, I can't talk to you, and I said, OK!