Crime and Gangster Films are developed around the sinister actions of criminals or gangsters, particularly bankrobbers, underworld figures, or ruthless hoodlums who operate outside the law, stealing and violently murdering their way through life. In the 1940s, a new type of crime thriller emerged, more dark and cynical - see the section on film-noir for further examples of crime films. Criminal and gangster films are often categorized as post-war film noir or detective-mystery films - because of underlying similarities between these cinematic forms.