Among them: Why was Ruiz killed, and what kind of training or rules could have prevented his death? According to your research, what rules are police officers following when they’re making decisions about when to use deadly force? They’re going to imagine the worst-case scenario because they don’t want to give the bad guy the first shot, right? Criminologist Franklin Zimring argues that police departments should write rules that tell officers when to refrain from shooting or stop shooting. They want to learn what rules officers are subject to.