Personal space

There has only been one time when I've felt unsafe on the subway, and there's only been one time when I've felt unsafe in my building. Both times have been when someone was invading my personal space.

In the subway, there were fewer than 10 people in the car, several benches with no one sitting in them, but this old man sat down right next to me. Unfortunately I was on a forward-facing bench seat and I was in the window seat, so I couldn't just stand up and move. I pretended that I was getting off on the next stop, then waited for the next train.

The incident in my building happened just today. The elevator showed up with just this one guy standing in it, all thugged out. Thug gear doesn't usually intimidate me in and of itself, but this guy was standing right in the middle of the elevator with a wide stance, like he's trying to look intimidating. I get in and greet him civilly, but he doesn't move! Usually one person stands in one corner and the other person stands in the diagonally opposite corner, but he was standing in the very centre of the elevator and didn't move at all, so wherever I stood in the elevator I would have been in his personal space. He didn't say anything, we just stood there like a normal elevator ride, but he didn't move at all.

I know that in some cultures personal space rules are different, but I can't imagine any culture where the norm is to be as close to another person as possible when there is plenty of empty space. I also know some people with mental/intellectual disabilities don't quite grasp personal space. What I'm wondering now is whether anyone has done a study of inappropriate use of personal space. I can imagine that someone might get in someone else's personal space in an attempt to actively intimidate them, but I don't understand why elevator dude would want to actively intimidate me - most people find me surprisingly non-offensive. Why on earth would someone want to get into some random stranger's personal space for no reason, thus losing some of their own personal space? It reminds me of some petty childish turf war. Is taking up other people's personal space just for the hell of it a sign of a psychopath?