My dad has personality disorder?

He is 50 year old. Sometimes he is like very kind and wise man but sometimes he want to kill me and he hate me. He attack my mom very often but few days later he become normal. He never talk to me like normal dad. I am high school student and i get C's. Sometimes when i try to talk about it with my dad he shout at me and calling me with bad words like *** ****. I am really frustrated. He is always in work 7 days a week. He is electrical engineer and he doesnt think anythink beside his work. He want me to become like him. But i bad at math. One day mom said that i cant be engineer, dad become insane and said to kill me. I dont know what to do? Help me?