I'm so glad that you have your son back, that he is free, and that you're the kind of good mom to be supportive as he goes through recovery.
If you can get him to trust a *good* therapist, a *real* therapist (ie---not a program quack), he's going to need a therapist's help coping with the post-trauma feelings. I'm a rape survivor, I know.
There are thoughts that it's natural for any survivor of this kind of thing---little niggling soul-destroying thoughts. If you don't get therapy for them, they can nibble away at you inside, bit by bit, over the years and really screw you up.
A *good* therapist will know the kind of thoughts to look for (survivor guilt, etc.), will find them, dig them out, rebut them with good sense that somehow as a survivor you can tell yourself all you want but it isn't the same as hearing it from a trusted counselor.
Good counseling, early, after a trauma like this can cut *years*--sometimes decades, no joke--off your recovery.
I'm glad you have your son back.
Best wishes with recovering from the experience and getting on with your lives.
Timoclea