Why do people like films/documentries on grusume murders horror and other vile things?

[Secret Asian Man]

Im not having a go its just I think its sick and I want to understand why people like it because to me I would have to be sick in the head to like it or be a killer myself but I guess I don't understand other peoples perspective!
Lol nice trollin ..NOT

Im not scared its just I wouldnt want to watch someone get killed or hurt etc