That has to be so horrible. I'm sorry.
If I was dealing with this in a child still in my home/under my care I would look into the Nurtured Heart Approach by Glasser (with a therapist if at all possible to guide us who had worked with kids with serious issues). I don't know if it would help but they've used it successfully with kids with serious issues like fire starting, juvenile delinquency, and the like. It's worth investigating.