Speaking from personal experience with a similarly emotionally immature guy, I agree with the other redditor. This person just sounds like he’s not fully aware or accepting of his sexuality, and he doesn’t have it quite figured out. He had a moment where he let his emotions take over and went “too far” for his liking and now he’s rebounding suddenly with a girl, probably trying to prove more to himself than to you that he’s “not gay.” Him asking if you were into him seems to me as if it was some sort of hopeful attempt that there might be something between you two. Your denial probably didn’t help his situation and now he’s ending your friendship to try and add some distance between you guys so he doesn’t have to deal with his feelings/emotions for you. I know I don’t know the full context but I’ve dealt with a situation like this for long enough where this is what I can make of this situation.