Does anyone know this Brain Teaser?

I remember in 9th grade my teacher would give us Brain Teasers before the bell rang. And the first one she gave I can't remember what the answer was, but it went something like "You're in a clroom and then you hear the teacher from the other room scream, and gl breaking. You run in there and you see the teacher laying on the floor dead, and there is a broken light bulb laying next to her. You run out into the hallway, and you see three kids running down the hall. What happened?" I would like you to either tell me how the Brain Teaser really goes, and give me the answer if you could.