Why is He trying to avoid me?

I have a friend who used to be warm and engaging towards me. He is a lot older then me and I sought his wisdom. But lately he has not tried to start a conversation with me and seemed to be avoiding me. I didn't make much of it thinking he needed his space or was busy or distracted by other things. But last night he pissed me off. I was talking with a mutual friend having a heavy conversation when he started calling her from the back of the room for her to come into the other room, taking her away from me. I can honestly say that I don't remember doing anything to offend him and I'm just about ready to confront him and ask him why he has been acting so snooty.