The entire group erupting into panic once Delilah reveals herself as an infected, with all the guys trying to will themselves into shooting her. And then Stokely bursts through the crowd and goes "I'll fuckin' shoot her!" and fires about five bullets in Delilah's general direction.
While it's Mood Whiplash, when the coach stabs the principal with a pencil he says, "I've always wanted to do that." The principal thinks she's made it to safety, locking him inside, another teacher stabs her repeatedly with a pair of scissors, and then says, "I've always wanted to do that."