Think about the dynamic in that household at the moment. Austin is fresh off his 200k++ loss, lost his sponsor, lost more free money, is in a sustained crack psychosis and is at the height of his paranoia because of trolls/addiction/mental illness/embarrassment. BossmAndrew is having problems with his own family and is forced to return home, and you know he has had several conversations with Ratdad about Austin being a druggie POS and the problems it causes. He saw Austin's room, the junkie wares all over the floor, broken shit, Austin has lost ~20lbs in the last couple months, and he stays up all night screaming and slamming shit. He talks to his parents like less than garbage. It could've been as simple as Austin yelling at Ratdad and his brother telling him to knock it off, and like eddie, the switch flipped and paranoid cracked-out austin started fighting with Ratbro for making him feel weird and not loving him. Scuffles happen.
What I'm really curious about is who called the police? Considering his parents are absolute tier 1 failures and the definitive example of enablers, I have a hard time seeing bossmom or ratdad making that call.