<human>: He needs help.  He recently tried to break my wrist to "express his dominance in the house" (his words) and my parents think it was my fault for provoking him because they know he gets set off easily (I asked if he had finished his homework, fuck me right). 

He has a large collection of knives but the most concerning part is the temper. It takes very little to set him off and he always resorts to violence. 

I am genuinely concerned that while I'm away, I will get a call from the police saying that my parents have been murdered.  

Years ago (maybe 4 or 5) I had to call the police on him because he was strangling my mother and he had to talk to a psychiatrist because the police were concerned that he didn't show any remorse.  

I don't what what I can do to protect the family and myself from an emotionally unstable person when my parents are too afraid to do anything about it.

Can you provide a brief overview of the text?
<bot>: I have a little brother who feels the need to "express dominance" in the family. My parents are too afraid to do anything about it. What can I do?