Driver of the pickup evidently didn't want to get involved. He didn't move the truck. Just let his passenger sit and be punched. After a while, the puncher stopped punching and walked away, wiping his tears. As strange a scene as that was, I can understand the puncher's crying.
Anger is a highly emotional state, and sometimes generates tears.
From playground games long ago I remember boys we used to avoid when they cried, because they were the meanest when they started shedding tears.