i could never predict exactly when it would happen. i would try to stop it from carrying out, or try to leave before it could be completed, but i could feel that some malevolence wanted me to be the recipient and wouldn't let me avoid it, and nothing i could do could prevent it, and my attempts amused it.
most of the time, the victims were my friends or students i knew well, because of course i was more likely to be nearby them without others around, though not always since the whole school was a well-acquainted network and everybody knew everybody.