You are having a really tough time. I just read the comment by 888mom and I wondered if it would be valuable to play that video to your son? It may give his some insight, and he may be able to see what the trigger was.
Have you tried getting a hidden video camera or something like that, and video tape him in the act? That way you'd have some proof. Sorry can't offer suggestions on how to stop it, but maybe if the psychiatrists believe you, then he can get some serious help from them.
Have you tried reading the health page about self injurious behavior? I believe aggression falls into that category.
I believe a lot of it comes with lack of being able to fully communicate what is going on in his head. Either he can't put his feelings into words, or if he can, he may feel like no one is listening... Or if people are disagreeing with him, he may be frustrated to that people "don't get it"
Also anxiety has a huge part with aggression (at least with me). The more anxious I am the worse I feel and I lose the ability to think clearly. The frustration of being unable to think clearly can set me on edge. In a complete meltdown, I lose rational thought process and go into instinctive "Fight or Flight mode” Either I attack or I run. Running is just a random open the door and I just take off and run...Although in the heat of it I feel like just running, even if I am about to hit a wall because I'm so focused on this awful horrible sensation like??? Impending danger (like imagine you just saw a tornado form right before your eyes in a thunderstorm or a huge fire burning up your kitchen). I still can't put that feeling into words. It's intense... I suspect every human can feel this same feeling if stressed enough. Just the stress threshold comes much lower for an autistic person.
The solution is to get him self aware of his own triggers. Once he can spot what upsets him, he can work on ways to reduce them. If it's something out of his control, it's going to be a bit tougher. This takes maturity and skill to realize I can't have everything in the world like I plan it out to be in my head... It doesn't happen. With maturity, skill, and practice successful autistic living requires the ability to adjust this mental image at a quicker pace. The quicker the adjustment I can make, the less stressed I am about the change.
I don't really have any experience of this, but no-one else has replied.
Are you involved with any support groups? If not it is worth joining one simply for the information that parents can give to eachother.
You say your son is okay within school, but could he be 'just holding it together' whilst he is there and all his pent up emotions come out at home? If so, what professionals are working with your son that could look at what is causing the behaviour such as things like stress or anxiety within school?? Is there any chance he is being bullied or teased at school?
Does he have any concerns about his future or aspects of growing up that he is not communicating to you.
If you feel it really is only at home, then what are the things that are causing him to get so angry/violent. As your son is verbal, have you tried talking about it (but when he is calm, not when it is happening).
Obviously it is not acceptable that he is becoming violent towards you and the family and he has to know that. But I don't know what the incidents are about so I cannot really comment on them. Is there any chance that he is being asked or told to do something that really is impossible for him to do, or impossible for him to do at that time because of Aspergers eg. obsessions? In which case a time out strategy might work better than demanding immediate compliance.
I'm sorry, I don't know anything about the medication your son is on and cannot comment on that.
Does he has any other co-morbid conditions as well as Aspergers? As he is seeing a psychiatrist are there any mental health issues?
I think more could be done by working with professionals, and it would help to know who is involved with your son presently.
But you need to try and get some indication from your son about what is going on. He may even be able to tell you what he needs to stop him reacting so violently.
Unfortunately the law is a pain in the backside. We had a similar situation with someone in our family circle who had mental health issues and was suffering from paranoia and threatening self harm. But again he wouldn't admit it infront of professionals and professionals would do nothing until he said he had this intent rather than the family saying so.
How things work in the UK is that most professionals are working for either Health or Education. If no other Health professionals are working with your son I would go back to the Pyschiatrist and tell them that the police route is not working and that it is totally unacceptable that the family should be in this situation and demand that she refers your son (or the whole family) to see if you can get to the bottom of it. If there is no professional involved from Education I would go into school and discuss who they could refer your son to so that they can do an assessment of him in school to see how he is there.
Is there a possiblity that it is not just your son who is having problems, but that there are maybe some family dynamics going on? Again I don't know if that is relevant because I don't have enough detail.
There is a system called 1-2-3 Magic which I have heard has been successful for familys with teenagers with autism/ADHD who were violent towards parents and siblings. It is a system that can be used on all the children. Again, there must be people near you who know about this behavioural system who could teach you how to use it. But I don't know if it is relevant in your case if there are other things going on besides Aspergers.
Hope this was in some way helpful.