My boyfriend relapsed last night

I haven’t been with him long, just about 6 months. He was clean from drugs and alcohol for 4 years. I stopped drinking and smoking when we got together and I was enjoying my sober life with him. He’s amazing. The best person I’ve met in a very long time. He was doing so well. Last night him and a few friends went to this get together and he came back to his house six hours later and he was acting all weird. He started yelling at me which he never does. He was acting so weird. Then I realized what was going on and I brought it up. He said he used and he doesn’t give a fuck anymore. Screamed at me to get out of his house and that he didn’t want to be with me anymore. He said he gave up and he’s back to using so he doesn’t want me around. This shit sucks. I’m so afraid for him. What do I even do. How do I deal with this? I know I can’t be around him anymore but I just don’t want to leave him to his own devices. I’m so scared.