You have a heavy cross, Mike. In all aspects possible, take the high road in what you say and do.
When your son chose not to remove himself from the presence of others who were considering illegal activity, and then participated in the illegal activity, he “crossed the line” with his family, with the legal and penal systems, and with God, of course.
I think psychologists “would have a field day,” since you’re in a facet of law enforcement and your son has chosen to break the law in a way that may involve serious repercussions for him, plus embarrassment all around. Perhaps interacting with him as though he’s an adult and fully on his own, and now calling all the shots, would impress upon him the severity of his actions? I have no idea. I’m guessing. A priest, a counselor, and a lawyer are essential.
-In regards to his arrest and what follows, I think that I’d tell him something like, “I’ll always love you, but you know that I can never condone what you’ve done.” I think that on the surface, I’d let him wrestle with the legal and punitive uncertainties, while working as much as possible behind the scenes to secure good legal representation. Since he’s a minor, it might help him most—wake him up—to face the music, depending upon what the likely penalty would be. You know your son and the juvenile penal system best. You certainly have my prayers.
-In regards to the baby, a paternity test should be performed as soon as that can be done. If the baby is his, it needs him and its paternal grandparents in its life as often as possible. Maybe part-time responsibility for a tiny infant would help him to turn his life around. Again, you, your wife, and son have my prayers.