Write it all down. Every incident that you can remember. Try to make a timeline of events and behaviors and system failures.
Start with the behavioral health folks. Tell them you can't handle him at home, that you and he are not safe, that he is a chronic runaway.
If he goes to rehab tell them the same thing. Tell them that he cannot live with you.
I had a friend in the same situation, her daughter was a substance abuser and a chronic runaway. She, at one point, threatened to burn the house down. My friend had younger children in the home. She refused to take her home from the mental health unit, they threatened to call child services on her. She let them. When she went before the judge she detailed everything that happened. Every incident, every failure of the system and they placed her daughter in some type of therapeutic residence. Her daughter is 21 now, sober, employed and going to college and has a baby boy.
