He Walked by Night is a 1948 American police procedural film noir directed by Alfred L. Werker and an uncredited Anthony Mann. The film, shot in semidocumentary tone, was loosely based on newspaper accounts of the real-life actions of Erwin “Machine-Gun” Walker, a former Glendale, California, police department employee and World War II veteran who unleashed a crime spree of burglaries, robberies, and shootouts in the Los Angeles area during 1945 and 1946.
During production, one of the actors, Jack Webb, struck up a friendship with the police technical advisor, Detective Sergeant Marty Wynn, and was inspired by a conversation with Wynn to create the radio and later television program Dragnet.
He Walked by Night was released by Eagle-Lion Films and is notable for the camera work by renowned noir cinematographer John Alton. Today the film is in the public domain. Wiki