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 in 1945 and 1946.