My boyfriend is not okay

I feel like I need to tell someone and I can't tell anyone we know because he asked me not to. I'm so scared and I don't know what to do. Yesterday my boyfriend came clean to me about some things he's been doing while I've been sleeping. He's robbed a house, a few cars, beaten up and violently harassed 3 groups of people and is now "hunting" a guy he saw talking to me. I don't even know if I believe half of it but I'm sick to my stomach thinking about it. I love him so much and I feel like I've lost him. I'm also scared for my safety because if I try to leave him or end things he'll be angry. I've been with him for 4 years and I don't want to believe this is real. I know I have to do something but I don't know what.