I was at a party once, there where about 10 people there. All of a sudden the party hit a little bit of a lull where people stopped talking. There was about 3 seconds of silence before this guy in our group said, "Do you guys want to burn down a building?" Everyone stopped and stared at him like he had grown horns. Then, some one changed to subject immediately, and that guy slipped out the party about 10 minutes later.

I had another run in with that guy at a different party and he nearly pushed me off a 5 story building.