City on Fire (movie, 1987)

Ko Chow is an undercover cop who is under pressure from all sides. His boss, Inspector Lau, wants him to infiltrate a gang of ruthless jewel thieves; in order to do this he must obtain some handguns; his girlfriend wants him to commit to marriage or she will leave Hong Kong with another lover; and he is being pursued by other cops who are unaware that he is a colleague.What is more Chow would rather quit the force. He feels guilty about having to betray people who have become his friends, even if they do happen to be killers, drug dealers, loan sharks and protection racketeers: "I do my job, but I betray my friends."To add to his problems, he begins to bond with Fu, a member of the gang.