GUYS PLEASE EXPLAIN--my ex boyfriend is acting crazy!?

So my ex broke up with me and said he wanted to be friends. After a couple weeks I decided to be friends too. We talked and it was ok then all of a sudden he started distancing himself and when I would try to talk to him he would reply very rudely. I was worried about him so I had a mutual friend contact him and found out he is really depressed. I want to be there for him but he has made it very clear that we can not be friends because I tried to talk to him (he doesn't understand I was only trying to be a friend and be there for him). What should I do?