"The Killer is Loose" is a 1956 B film directed by Budd Boetticher, and it's pretty good. It stars Wendell Corey as Leon Poole, a man who is working in a bank when a robbery occurs. It doesn't take long for the police to determine that he's the inside man. They go to his house to arrest him, and he refuses to answer the door, shooting through it. The police break in, the lights are off, and Detective Wagner (Joseph Cotten) sees a form emerging from the bedroom and shoots, killing Poole's wife. When Poole is sentenced, he promises to pay Wagner back for killing her.
I've never understood what happened to Joseph Cotten's career, but by the '50s, he was appearing in B movies after being part of so many important films in the '40s. He's good in this, as is the beautiful Rhonda Fleming, who plays his wife. Corey is excellent as Poole, a disturbed man with a flat affect; he never knew any happiness until he got married and goes crazy when his wife is taken from him.
Good noir.