Planning after school

The story is about an after school class that gets attacked by an unknown killer but little did the killer know there was a psychopath among the students one of the students is a diagnosed psychopath who has more of a killer instinct then the killer himself. He convinced the other students to attack and kill the murder to " survive " but really he wanted to feel how good it really feels to kill. And after the taste of killing he WANTS MORE and so he became The School Killer