Yelling "Fire Extinguisher!" In A Crowded Classroom

In the middle of my first class today I heard a commotion outside. I peeked out the door and saw what appeared to be a cloud of chalk dust and a number of children running around, while my fellow teacher looked on with a grim expression. Luckily, our classrooms all have CCTV for training purposes, so we were able to watch the replay. A student was supposed to be writing an answer on the board, but instead this gem of a pupil decided to play with the fire extinguisher, with predictable results.