There was just an article about a woman who shot a man after a road rage that resulted in an accident. You would have to be crazy to approach a person's car in traffic. I agree that there is a huge part of the story missing and the passer should have called the police.
People call 911 because the have locked themselves out of their car and because there is a raccoon in the back yard. Not shocked by her caller for someone passing in a no passing zone. Now that everyone has a cellphone 911 is increasingly abused and under funded.