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 a 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 between 1945 and 1946.

Alfred L. Werker was a film director whose work in movies spanned from 1917 through 1957. After a number of film production jobs and assistant directing, Werker co-directed his first film, Ridin' the Wind in 1925 alongside director Del Andrews. He was brought in by Fox Film Corporation executives to re-shoot and re-edit Erich von Stroheim's film Hello, Sister! (1933), co-starring Boots Mallory and ZaSu Pitts.