I don't know what to do

My boyfriend and I had a huge fight. He kicked me and our 5 month old daughter out at 1 am on Sunday. I have scratches all over my arms and neck. He punched a hole in the wall, he punched the tv and he broke my diamond necklace. It was late and I didn't want the police to come so I kept trying to tell him to lower his voice and he got so frustrated that he grabbed his unloaded gun and put the clip in it. I then ran and grabbed the baby and locked the bathroom door. I didn't have my phone so I had to run to grab it and called my mom to pick us up. I didn't want my mom to know the full extent of the fight, so I just told her that we broke up and we're never getting back together. 
I'm a SAHM so he's the sole financial provider and all I have is $20, a half a box of diapers and clothing. He has both me and our daugther social security cards. He won't answer my calls. I know I should've called the police. He was in a terrible car accident before we dated and he has some head trauma so he gets extremely angry at the smallest things. 
I've never left her alone with him because he's not comfortable and I'm afraid that he'd try to take her away from me just to be spiteful. 
I just don't know what to do. 
He called my mom and told her that he wanted to see the baby and I packed her a bag and he picked her up. He wouldn't tell me what time he would bring her back. She's exclusively breastfeeding and so I didn't pack milk because I didn't want her gone all day. He asked for the key back to the apartment, so tonight my sister is taking me to the police station so we can have a police escort so I can't get the rest of my stuff. He doesn't want to talk to me about the baby so I'll just have to take him to court.