1948 He Walked by Night

This film-noir piece, told in semi-documentary style, follows police on the hunt for a resourceful criminal who shoots and kills a cop. In post WW II, Los Angeles, a cop's killed in the middle of the night. With no leads, the chief of police assigns Sgts. Jones and Brennan to investigate and apprehend the killer. They target low-level criminals, such as Paul Reeves, hoping he'll lead them to bigger fish, specially, the one who shot and killed the cop. Technical advisor for the film was Sgt. Marty Wynn of the Los Angeles Police Dept. During the course of shooting, he fell into conversation with Jack Webb, then the star of radio's "Jeff Regan, Private Investigator", who had a small part in the film. Wynn suggested that Webb do a radio series based on actual police files. Thus was born the idea for "Dragnet," which debuted on NBC radio about four months after this film was released.