CNN Anderson Cooper 360 June 6, 2014 03:53:00
Sound. everyone i've talked to said they only heard one. and then that's kind of when everything started. >> so you heard what sounded like a muffled sound. you said you think there was only one. >> yes. >> did you know -- i mean, did people know instantly what was going on? >> actually, no. all the students thought it was a gunshot. and i was in physics and my professor thought it was an experiment because -- okay, i can see how it was that. but someone next to the door, they look out the door, didn't see anything but they heard something and they come back in. said, i think someone was shot....