Really? I thought he was going to murder me so I shot him in the face with a shotgun and he went down in one hit. I didn't even hesitate.
I used to get bored after finishing the game, and one thing I'd do is test that guy. I'd stand still and watch him. If I had the PC version and the right knowledge, maybe I could have the RPG early and try shooting him point blank. XD
Meanwhile in Infinite: WEEEEEE SKYLINES OH stuff MISSLE ZEPPLINS!
They're called Security Zeppelins. Also, I'm pretty sure it's hard to get hit whilst on Sky-Lines by those, although it isn't out of the question. I'm more scared of flying at guys on the same side of the line, but I think the two sides work differently.