The father of my son is trying to take my son away out of spite and I would like to know the best way to go about this situation.

The father of my son has been very emotionally, mentally, and emotionally abusive. He's raised his fist to me a few times and has began pushing me. He would call me names almost every day and it kept getting worse and worse. I finally decided this wasn't the life I want for my son and I so I told him we were done. He told me if I left him he was going to ruin my life. He's said things like "If I have to suffer, so do the two of you," referring to my son and I (which my son is 7 months old). No custody agreement has been established and hes been making threats since Thursday. He tells me he's going to call the cops and cps. He wrecked the apartment and is telling people I did it. He's also telling people I stole money when I did not. I've never been in a situation like this and am afraid of what he'll do next. He keeps asking me where our son is and I tell him I don't want to tell him because I'm afraid for my son and I. When I won't tell him the threats begin. What should I do?