Agreed. But, the mom says he is mentally ill and that he's been refusing to take his medication. I will take her word for it.
That does NOT mean his behavior is excusable. It just means that maybe she has been doing the best she can, but now she can no longer control him. In her shoes, I would send him to live somewhere else where his behavior can be controlled. This is too dangerous now, not only for her but also for her other child(ren).
Went thru that with my co-worker who’s son wouldn’t take his medication....it’s very common they won’t. Hpwever then that’s the time for institutional living which it’s long past this for that mother - this is not his first time.