You are new in school and you’ve recently seen this one male student everywhere. He doesn’t do harm..right..?

One night you are walking back home when you see a male in an alleyway covered in blood. You’ve also been recently noticed that the males and females you’ve talked to have gone missing or found dead. Right now you are at school when you noticed similarities between the male and the male covered in blood. You are in class right now, he’s sitting behind you, What do you do?