The Long Day of Inspector Blomfield (1968)

Inspector Blomfield catches a thief who has a fatal accident while trying to escape in his car. A short time later, his drug-addicted brother Johnny enters the police station while Blomfield is investigating a murder and threatens to blow himself and everyone else up with a bottle of nitroglycerine. By the time Blomfield arrives at the station, the maniac has been overpowered by his colleagues.