What most cops don' t understand is that lag time takes place at least twice in violent confrontations. Officer action often lags behind subject action during the initial attack and at the end of the conflict which most often the police end. Even when a suspect stops threatening action, he or she may still be subjected to a police counter action. The recent incident in Philadelphia, caught on video and beamed across the world, is a good example of lag time. The officers reasonably believed the suspect was dangerous after being told he was a robbery suspect, had shot a police officer, and caused a high-speed chase while driving a stolen police car.
Danger is part of the police world and so is the duty to protect, i.e., stop the danger.
Officers interpret the suspect's actions in order to counter or respond to the violence. The officers' response is often characterized in reaction time. Reaction, while appearing to be immediate, takes time. The officer must recognize, interpret, decide and act in order to respond. Add many signals and stimuli, to be interpreted in a dynamic violent situation, and it is no wonder that some cops are still acting as they were trained even after it appears the suspect has ceased action.