My brother

Just from reading responses and such, I would ask if he would have a family talk, with the support of your parents. you guys can discuss how he is letting anger get to him and destroying things unintentionally. Most people with issues like that, will not accept help unless they come to realize that they wont get replacement stuff and its of monetary value at their expense. you can destroy things you dont pay for, it wont bother you. destroy stuff that you worked hard for, and its a different story. id see if that route works

 

As others have said, you definitely need to talk to him first and try to have a breakthrough with understanding. I recommend explaining in the beginning that the conversation is out of pure concern and not to bitch at him. Explain that in the real world, reacting this way will only get him in trouble. If he's 17, any legal mistakes can be ruled as adult. If you can, try and get him into some counseling to see why he's so angry. Again, just keep reassuring him that the conversation is only of benefit to him, and that you want to help. That's the best way to get better results.

 

My brother did the same thing until he turned 19, bad anger issues. Broke his gender guitar once in a fit. He should grow out of it but you never know