What is the short summary of the story "Police Rat" in the collection, The Insufferable Gaucho?

Police Rat, tells the story of Pepe the Cop, a rat living in the sewers and working as a police officer. Investigating the deaths of several dead rats, Pepe comes to the uncomfortable conclusion that a rat has been killing other rats—something that has never happened yet in the rat kingdom. Pepe the Cop confronts and kills the murderer, but knows that these deaths are the beginning of a moral and social decline in the rat kingdom.