Why is he suddenly rude/weird?

I don't even know how to begin this. At my age, I figured I'd seen everything, but haven't encountered this crap before. I have a work colleague/friend who has suddenly started behaving erratically. I assume it's work, but he won't talk about anything. Everything is "fine", so I didn't press it. Just chit chat as usual. Twice now, I'd been talking with him, and things seem normal, but all of a sudden, he freaks out about something that was said, and lashes out. I had a door slammed shut in my face a couple weeks ago because he got super defensive, claimed I (and everyone else) want him to fail. I stupidly said that that's BS, and cared about his feelings. I don't even remember what started the whole thing. So naturally, slamming a door in my face is the appropriate response. He doesn't do this with anyone else.

I've given it a couple weeks, barely interacting except for a hello or the blike if we see each other. Basically cut him off from non-work related things. Went on a hike with a work group Saturday, and we ended up being in the same vehicle, alone. Thought maybe it would be normal, or a good way to reconnect, something. Nope. He was teasing me/making jokes at my expense most of the way, and harping on some ex-coworker who is a "pervert"... among other sexual topics (this is relatively new coming from him, as well). Don't mind a little playful back and forth, but this wasn't that. I barely said anything because if I did? More jokes/comments.

At this point, I'm done. I know it isn't me, but it IS me he's chosen to behave like this toward. If I could ask him, I would. I feel bad because this has come out of nowhere, and I thought we were friends. I looked up to him and trusted him; he's also older, so I think that plays into my shock at the behavior. Have any of you dealt with something similar? Wtf?