All of this sounds extremely alarming. Hitting holes in walls, attempting to assault people including his own sister and screaming in rage are signs of some major, possibly dangerous anger issues. I would take these signs very seriously.

I think you guys need to take whatever steps to protect yourselves, so that you can continue to help him. It sounds like he definitely might hurt someone in the future and a mental health warrant might be due to protect everyone around him. What it means is that he can be taken into custody for a mental health assessment by law enforcement, if he won't agree to go in voluntarily.

I'm definitely no expert with these cases though. I had a friend who was borderline and she tried to attack me with a razor when I tried to stop her from cutting herself, so I know how helpless you must feel right now though. We want to help our loved ones within our own family/peer unit but sometimes we just don't have the resources to deal with things like these as a family. :/ Anybody else have some ideas?