Hey what's up?

I just got out of class and I was walking back to my dorm when I saw my RA. Being that he's my RA and I should be nice to him (I don't know him that well, but he seems like a cool guy), I say "Hey" as he was about 5 feet away from me. His reply was "Hey. What's up?" but as he said it he was right next to me and continued to walk in the opposite direction. WHY DID HE ASK ME WHAT'S UP and CONTINUE TO WALK IN THE OPPOSITE DIRECTION. I realize this happens a lot with people. Usually if it's a close friend I'll turn around and I'll be like "Nothing much you?" and usually they'll respond but won't turn around. Then I say "See ya later." THIS PISSES ME OFF SO MUCH!!!!!!!!!!!!!!!!!!!!! Don't ask what's up when your passing someone by. If you're going to stop for a second for an answer then ask if not, JUST RESPOND WITH A HEY!!!! That's all you need to do. I say "Hey" you say "Hey" that's it... (Jeff Dunham flashback "I talk you talk that's it" Peanut ... Spark of Insanity video). K over it. short rant but a rant anyway. lol