The only thing I can suggest is that his medicine needs to be upped. I wish I could be more help but my Aspie is a girl and hasn't shown any agression so far. I know that anytime a new med is introduced, it normally takes about 2 weeks to see how much of an effect it will have.
My nine year old nephew, who has recently been diagonsed with mild autism is also aggressive. His behaviour mainly happens at school and is often targeted from being bullied. He cannot control his anger and has no snese of humour and cannot handle jokes or being joked with. He often talks about stabbing and killing, which is very worrying. I am looking into further help and will post any information I have when I receive it. If anyone else can help, please post information.
Finally school starts thinking that maybe something bothers him in school.And starting Monday they will change class.In this school year I change 5 medication and nothing works.Then I ask school everything is OK in his class they always said- yes.Now I think it wasn't the truth.Let see what Monday brings.They always think what autistic kids are retarded.
As an autistic young adult, let me come at things from a slightly different angle. Aggression for me was a sign of frustration, but mainly of anxiety. The whole fight/flight mechanism is applicable here. The school calling the police would only heighten his aggression, that wasn't a good move the the school's behalf. It could also be that school is simply too noisy for him, and that it causes sensory "overload". When that overload as at its greatest, Austistic people like myself are more prone to aggressive bahaviour.