He Walked By Night (1948) | FILM NOIR/THRILLER | FULL MOVIE

In post WWII, 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.

IMDb: https://www.imdb.com/title/tt0040427