My son bullied another kid

I just learned that last year my son (13) was part of a group of kids that bullied another boy in their social group.The other kid ("Chris") was a bit of an odd kid, but he always seemed nice to me. My son never said anything about bullying, however, so I never thought anything of it. Just thought he was a kid he hung out with.The other day, my son told me that Chris isn't in the school anymore and he didn't know what happened to him. He just stopped coming to school. I said that I could get Chris' parents number and he could reach out to him and maybe they could hang out. He agreed.Then, later I saw that he had texted another friend saying that he was getting Chris' number so he could apologize to him. Clearly my son feels bad about Chris but hasn't confessed to me about what happened.Chris' mom works in a shop not far from our house. Today, I drove by and chatted with her. She explained that they pulled Chris out of school and are now homeschooling him. Apparently it was pretty bad: Name calling, taking his stuff, throwing away his food, etc. They didn't pull Chris out solely because of the bullying, but it seems like it was a pretty big part of it. Anyways, I apologized for my son, got their phone number and said that I would give it to my son.I can tell my son feels bad about Chris. He's usually a sweet kid, so I'm pretty shocked to learn about this. He has a disabled sibling and is very kind with him. (So much for all the anti-bullying campaigns they subject the kids too.)What is my best play here? He clearly knows that he did something wrong and feels bad about it. Should I make him call and apologize? Should I let him deal with it himself?Anybody have some useful advice?​ via /r/Parenting https://ift.tt/2tF3gGk