The Bad Samaritan

In "The Bad Samaritan", we learn that David Cash is being hated by the people and is also being the blame for what happened to the little girl. In my opinion, I believe that none of what happened was his fault because he was just trying to avoid problems and wasn't trying to get involved. I think that he knew what was going to happen but he did give a warning to his friend and decided to leave. I don't understand why people thought that he should have also been charged if he didn't do anything to the little girl. He should have said something but then again, what if his friend would have also tried to hurt him. Maybe David was scared to avoid things because he didn't know the reaction his friend could have had.