A question about dating. I need help.?

I like this guy that I work with (Chris) but he just got out of a year-long relationship with some other girl I work with. She dumped him with absolutely no explanation and he is heart-broken. I started hanging out with him and one of his guy friends (Don) who happens to be yet another co-worker. Don told me that Chris likes me and it is quite obvious when we go out. Kissing me and dancing with me and everything, which is great. The thing is...Chris is not over his ex. I really like him and I don't know what to do. He says that he wants to take it really slow, but he is so hard to read. I don't want to act like I care one way or another but it is getting to where I do. So do I wait to see what happens or do I just move on? How do you try to date someone whose heart is broken?