Stray bullets and accidental shots are just as lethal as aimed ones. The point is that someone pulled over at a traffic stop can keep a gun hidden and take the first shot if they want to. Each and every traffic stop is a nervous bundle of potential danger for a cop, and they aren't paid to endanger themselves. That's why we go out of our way to make cops comfortable during a traffic stop. Keep your hands where they can be seen. No sudden movements. Polite interaction.
It's not healthy to be near nervous cops.