What can I do about this friend?

My friend just broke up with his girlfriend. He was always telling me how he was really in love with her and how he’d always be there for her. I honestly thought they were cute together, even though I secretly liked him.

Lately he’s been really depressed and drove to doing the worst thing ever thought of, cutting himself. I saw him bleeding in English today, and in Science, he was crying and cutting himself. I’m really worried about my friend.

What should I do? Should I let nature take it’s course? Or help him? He says there’s nothing wrong, or he just doesn’t want to talk about it but I know when he’s not okay.