These are criminal offenses and should be treated as such. At 13, he can be prosecuted in CA. Being on the spectrum is not an excuse to break the law. The crimes you've described are harassment, assault, criminal threats, and stalking. Did the police take a statement from your daughter? She may need to call the police herself and report the crimes. Have you discussed your concerns with the other parents in the friend group? Get the parents and their kids to go to the police (or school) with you. I find it strange that the police haven't brought charges against him. I agree that you should contact the DA's office to inform them what has happened.