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(CNN) - When gunshots rang out at Arapahoe High School, one young student told CNN affiliate KDVR News that he didn't know what they were at first. But once they heard the repetitive sounds, he and more than 20 other classmates followed procedure.
"We turned off the light, and locked the door, so they can't get in. And we make sure that if we hear anything ... we won't go out until the SWAT team comes and opens the door," he said.
In that dark room, the teacher tried to calm the students down.
"A cpuple people were crying, and we were just all in the moment, we couldn't really think, at all," he says.
Two thoughts went through the young student's mind.
"Am I going to get out? If I do, what's going to happen afterward?"