What should I do about my dad?

My dad gets a ton of stress at work and he always takes it out on my family. Just today my mom accidentally hung up his phone call and he just totally flipped out at my mom like screaming and cursing her off. Its a lot worse sometimes though, and sometimes so he gets so insanely mad i end up crying hysterically (which is really rare for me being 15) but whenever i start crying or anything he just gets even more violent and ends up like pulling out my hair or throwing me against a wall or something and i cant take it anymore! I dont know what his problem is but he just always umes he's right in what he's doing and can do whatever he wants. What can i do to get this to end?