Why would he do this?

I’ve been dating this guy for three years. He was always perfect until about a week ago and he’s been kinda mean to me. I confronted him about it and told him I wished he treated me better and he blocked me and said go find someone better then. Idk what happened. It was barely even a breakup and we didn’t even have a full conversation about it. I texted him on fb and asked was he going to unblock me because I wanted to discuss what happened and he said no and blocked me on there as well.