Because they're all worthless lowlife scumbags that have never been taught respect for anything or anyone. I've always said they should all be put into the army & taught some discipline because obviously their parents didn't teach them any.why do they do things like this!!!
If it happens again, call the cops. If they wont come, take photos. It might be a gang of them or it might just be 1 lone dirtbag with nothing better to do with his sad life.