18 Year Old Brothers Violent Outbursts putting family in danger

My 18 year old brother is autistic and the older he gets the more violent and volatile he has become despite being showered with love and attention his entire life. He has been on medication and using talking therapy for most of his life but they have not curbed this behaviour.

He has recently physically attacked our mother and other brother and regularly attacks our father. He has threatened the family with knives on multiple occasions.


He devolves into intentionally provocative language (sexist, racist) during his “rages” which is not something he has grown up around but I suppose wants to get a rise out of people. This is often followed with physical attacks. 

He has developed a particular grudge against my mother who has dedicated her life to caring for and loving him. 

The police have been involved multiple times but won’t arrest him as he is very polite and remorseful after these outbursts and claims to be afraid of himself in those moments and he wouldn’t be sectioned by the hospital due to Autism recently becoming exempt from the mental health act. 

What can be done? I am afraid for my mother’s life if things continue on the path that they’re on. How bad to things need to get before someone steps in to help?