Ex boyfriend issues, why is he being such a jerk?

Ok so me and my ex brokeup almost 1 week ago, and it was pretty much a mutual thing. But now he has a new girlfriend which I am ok with because she is pretty cool and I really like someone else. Anyways so he has a new girlfriend and its really wierd cus...

he was their with her and like they would b sitting down most of the time, or she would be dancing and he would be sitting down and everytime I would walk by to get water or something hed look up at me and just stare. And like he just kept staring across the room at me, and it was really wierd. I always thought that if we brokeup we would still be friends, he said he would want that too,until we actually brokeup. Because now hes spreading rumors about me, and last nite he messaged me this really rude message about how I have stuff in his locker and he wants it out. I understand that he needs my stuff out, but the way he asked it was just really mean. And so anyways why is he being like this? I mean he thought we should breakup 2 and he has a new girlfriend, so anyone please help?

well he probably didnt want to break up. and he said he did because you wanted to and now that you are he's bitter about it... just call him ask him to meeat you somewhere to talk and let him know how he feels be open not contradicting and see how it works out... who knoes maybe you can get back together again or maybe you can just be good friends you have to talk it out first.. or if you really dont care screw him and dont bother talking hah

I know what hes doing hes trying to me you jelous so ull want to get back with you just tell him theres no way to et back together or if you still like him get back with him