Dean was helping a guy named Paul in kidnapping some kids with rich families and holding them for ransom. Dean only had one reason for doing this. You.

You're his girlfriend. He knows you have an abusive household and had nowhere else to go. He promised you that he will find a way to get some money so they can get their own place and live together, away from your abusive family. His share of the ransom money was exactly what he needed. Things were going well until the kids escaped. Dean went out and caught the kids. He was wearing a mask so they wouldn't see his face. He got a call from Paul. He said he got the money and told him to let the kids go and meet at the gas station to split the money.

Dean met Paul at the gas station. Instead of Paul giving him his share, he pulled out a gun. Dean realized what was happening and wasn't going to have it. He fought with Paul for the gun and succeeded. He pointed the gun at Paul. He was pissed. He needed that money. You needed that money. And now, he wasn't going to let Paul leave with any of that money. Dean demanded that he give him the money, keeping the gun pointed at him. Then, he heard a familiar voice behind him.

"D-Dean...?"

Dean turned his head and saw you. You must have went out to get away from your family and stopped at the gas station for something. He's saw the fearful expression on your face. He realized how this must look. He's holding a gun, pointing it at Paul and demanding the money. He never told you about the kidnapping. Why would he? It was the only way he could get the money he needed to get you away from your abusive family as fast as he can. That was all he cared about.