The Night Man — K.W. Jeter

Steven is the scrawny kid who hangs around with the football team, suffering their bullying and teasing. He imagines what it would be like to have a friend looking after him, but before long it is not just his imagination as horrible things start to happen to members of the team.

Poor little Steven was puny and shy. Everyone picked on him, from his drunken mother to his sister and her superstud boyfriend. Steven could have used a friendd one up. And if an awful lot of people had to die in terrible ways . . . well, what are friends for?