Petrosino was an Italian-American detective in the New York City Police
Department in the early 1900s who was assigned to investigate the
Mafia, an Italian organized-crime group that was well established in
the immigrant Italian community in New York but about which very little
was actually known. Petrosino's investigations resulted in many arrests
and convictions for extortion, robberies, murders, etc., and exposed
the organization to the public. He was sent to Sicily to work with the
Italian police to investigate the connection between the Sicilian and
American branches of the Mafia, but he was assassinated by Mafia gunmen
in Sicily in 1909.