What should my mom do ?

I came home from a party and I walk to the kitchen and my mom says "he threatened me" ("he" is my dad). I'm not gonna get in detail but later on in the night she basically told me that he said that he would knock her out and go to prison for it. But he didn't actually do it. What my mom had to say about it is "I wanted all my kids to know" what should my mom do ?