Your Prisoner is Dead - S1.E7

As he is on an erand at the drug store, the chief witnesses a robber hold up the place. When the robber turns his gun on him, the chief shoots him in self-defense. However, when he finds out that his prisoner has died, he thinks seriously of retiring from the police force since he has never shot a person before. In the end, Nell convinces him to go back to work, when she makes him realize that he really is a pretty good cop.