my father almost hits my mother?

Well, I'll make it short. I'm 15 and my father smashed a saucepan on my head. My mother dragged him away and he was gone for a while. He came back at some point. My mother said she was only living under the same roof with him because of my little sister, which was all well and good, but a week later he almost hit my mother. He almost threw a table at my mother and my mother screamed for help. I rushed over to him with a butter knife and told him not to touch my mother. He freaked out, but my mother held him back. After that, they continued to insult each other and argue about a robbery that is still unknown and was probably caused by my father, but that's just my mother's suspicions. I'm asking for urgent help.