Roommate in college grew up as a missionary kid in papau new guinea and was definitely a candidate for PTSD from seeing some very violent shit.
That said, the first incident occurred one night when I told him I wasn't going to come home that night after closing down the blockbuster I was managing. Plans changed and I came home. He had set up warning alerts for the front door of the apartment - warning being a cup of loose change and a stainless steel pot below to catch and make noise. I come in, sit down, and watch a movie. It's now like 3am and I go to enter the shared bedroom/think dorm room with twin mattresses borrowed from the school for the summer. I open the door and he flings his blanket off and sits up dramatically and aims his rifle directly at me and from roughly 10 feet away. I yell at him and tell him to put the shit away, it's just me. After a few seconds he realizes it is just me and sets it down. I don't sleep that night.
Next incident, I forget the trigger for it and he ended up pulling his shotgun on me and chasing me around the apartment complex, tennis courts, etc. laughing a maniacal laugh while I'm telling him to put the shit down and not be insane. Pretty sure he also stole my SUV's CD/Stereo.