When Filch wasn't guarding the scene of the crime, he was skulking red-eyed through the corridors, lunging out at unsuspecting students and trying to put them in detention for things like "breathing loudly" and "looking happy.
J. K. RowlingGeorge: "I can't see anyone trying to bump off a quidditch team." Fred: "Wood might've done the Slytherins if he could've got away with it.
J. K. Rowling