[Lelola]

A. I think he was either visiting friends or a girl in your complex and didn't want you to know. I would lean towards a girl. If an ex called me and said they saw I was near them, I would be a little bit creeped out.

B. As if saying "what's new," that's kind of general thing I will ask people that I see if I haven't seen them in a long time or if I don't really want to talk to them but can't exit the conversation. He may have been trying to be nice.

C. What if he doesn't talk to you because he does not want to talk to you? That is something to consider.

D. Changing the profile to friends only is generally a sign that he doesn't want you to see his profile.

I would try to distance yourself from the ex. I think he did the right thing in changing his profile to "friends only" but he also should have been more upfront.