My ex boyfriend is still heartbroken. But I have no feelings for him. What do I do?

I dated this guy a while back. I guess I was the first girl he really got attached to. I was the first girl he kissed, I took his virginity too. We saw each other like once in every few months. He lived far away in another town but we still continued dating. But we broke up because I felt like we didn't talk very much anymore, he claimed he was busy but I just couldn't deal with a long-distance AND sort of busy relationship. It was just too much for me. He got angry and cussed at me. So now I have been dating a different guy, I really love this new guy. I can say I do not have ANY feelings for my ex boyfriend anymore, but people say he has been depressed and angry since the breakup. It's been 9 months since we broke up. I feel like I broke his heart. I try to be nice to him, but he seems really irritable. I feel bad. He messaged me on facebook a week ago and said hi. I didn't reply because I can't think of what to say. What should I do?