That is something that your child and his father will have work through together. You can try to do everything in your power to push the two of them together, but it won't work. Your son was hurt and needs time to work through that.
Depending on the severity of the child's case and the access you have to mental health benefits, the syndrome can be reversed and mended. It's important that both parents have a big part in the process, though.
It seems like he has some resentment with his father and it may be best to try and do things as a family, as hard as this might be it would be what is best for your child.