Change of Heart...Attack?

From an unnamed university in the greater San Francisco Bay Area...

So this one faculty member has the reputation of being a curmudgeon with the heart of gold; a dedicated teacher who genuinely cares about his students, but will harass and insult them incessantly regardless. He often comes into our office to mock us for having yet another meeting, to tell us we send out too many emails, or to blame us for something that is totally not our fault.

I find him alternately annoying and amusing. I know his bark is infinitely worse than his bite, and as someone who likes to pretend to be meaner than she actually is, I respect his game and try not to salt it. However, sometimes he's just a genuine asshole. When he's in a relatively good mood, we have a fun, joking relationship based on mutual insults. When he's being a prick I cannot stop myself from yelling "GET AWAY FROM ME YOU COLOSSAL JERK!" He never can tell if I'm kidding or serious when I have these little outbursts, which is probably for the best, because I always feel guilty after being so rude to someone who's the same age as my dad.

Anyway, he's recently been super nice and pleasant to work with: responding to emails without the slightest trace of snark or resentment, volunteering to complete tasks instead of whining about being asked, and even sticking up for me when another faculty member criticized my work. I really don't know what to make of it. I'm kind of afraid that he's dying. He's diabetic and smokes like a chimney, so it's not totally out of the question.

I'm also disappointed because, with him being nice to people these days, I am totally a front-runner for biggest jerk in the building. I'm totally more upset about this guy potentially dying of course, but seriously I can't think of anyone meaner than me if he's out of the running. I might have to start baking shit for people, or at least looking them in the eye when I pass them in the hallway.