I'm so sorry. 
When easy child was 10 and severely depressed and very hostile, I couldn't leave him and difficult child alone at all. After he choked her and she had red marks on her neck, I let him know, at 10 years old, that if he touched her again I would call the police. That was hard.
Had he been older, I would have been afraid for my safety.
I hope you're able to find a solution quickly.
(((hugs)))
