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, is loosely based on 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 in 1945 and 1946.During production, actor Jack Webb met the film's police technical advisor Marty Wynn and was inspired by a conversation with Wynn to create the radio program Dragnet, which later became a television series.He Walked by Night was released by Eagle-Lion Films. The film is notable for its camerawork by renowned film noir cinematographer John Alton.Today the film is in the public domain.