My Brother Is Violent.

I (15) female live with my brother (17) male and my mom. My brother is violent and has hurt both me and my mom on multiple occasions. I could almost describe his behavior as bipolar in a way. Today there was a mild argument between my mom and him, nothing unusual for our house, when suddenly he races out of his room and fires a gun at the ceiling. He had shown this gun to me earlier saying it was real, then about an hour later saying it wasn’t. To me it sounded like damage control, like he didn’t trust me anymore to know it was real. Either way, he fired it at the ceiling, then drove away. I am scared but this sort of violent outbursts is kind of routine. The police have been called on him before but I think my mom lied to protect him. We couldn’t find a bullet hole, so it could have been a blank. He texted me like 5 minutes ago asking if he hit the dog and if she’s okay. I don’t know what to do, all I know is I don’t feel safe living with him. I can’t drive but I figured I might uber one day to a police station to build a case? He tbh needs to be arrested but the police don’t seem to be doing anything. I do have some video evidence of him being violent but all pretty blurry. I don’t know what to do. Please help.

edit- i live in PA