Examples of mafia violence can be seen in Coppola's Godfather (1948).
As seen by displays of public behaviour, power, stereotyping (Godfather 1948, 00:41:06-00:41:08)...
Note: after the first mention in your writing you can just use the film title.
Title, Year [material designation]. Subsidiary originator (if applicable e.g. Director). Production details
Godfather, 1948 [video]. Directed by Francis Ford COPPOLA. USA: Paramount Pictures
If you are referring to a particular scene or quote, you should include in the citation the time(s) (hours, minutes and seconds) between which it takes place in the film.