Cold walking

So my boyfriend and I got into a fight at his mothers house. He told me that he'll wait outside for me so we could leave. I told him I'm  not ready yet, he walked out anyway. I go outside a minute later and he's no where insight. So I get in my car and go in the direction of our house. I see him walking, it's 41 degrees outside. I pull up next to him and tell him to get in the car. Next thing I knew I got a call from his mom chewing me out for making him walk. That's what he told her. After I get off the phone with her, I try to convince him to get in the car for 5 minutes, he refused. Then a sheriff shows up and asks if everything is alright, we said fine and he left. He walked along side a wide road but then it merged into a one lane road. I had to leave him there. What do you guys think I should have done??