My little brother is having anger issues?

okay my brother he is 12 has mental health issues and today my youngest brother 5 years old broke his last nerve ( not letting him play the x box 360 ) and he started chucking stuff at me i didn't mind it until he start at my little brother with shoes and almost with a piece of wood for the fireplace then i started after him to get him i got him by the shirt and pinned him beneath my legs and started to yell at him and his face hit with my wrist now he threatening me with cops saying i punched him in the head how can i prove my point if he does call that i did not hit him ?