Y would a guy ignore you and be mad and joke around with you all of a sudden?

There where horrible rumors going around and a guy in my class believed them and began ignoring me for weeks. After spring break though he joked around with me and was nice when he wouldint even look at me before. Then the next day when I was sitting with friends he talked to all of them (he doesint know them) and then comepletely ignored me but walked by extra slow. Before he told me he was so "mad and annoyed" at me for that stupid rumore but if he's so mad and annoyed, y is he doings this now? I'm confused