A rising bookie after Mickey Cohen went to jail, Cahan prompted a Gangster Squad investigation and a court decision that changed the ground rules for policing in California.
The dapper former boxer came to town as muscle for Bugsy Siegel and emerged as L.A.'s most high-profile mobster of the 1940s and 1950s.
JIMMY 'THE WEASEL' FRATIANNO
Rounded up in early Gangster Squad roust, Fratianno was allowed to stay in Los Angeles and became the mob's top hit man.
Hired as a security guard at Cohen's home, Hawkins secretly served as a Gangster Squad informant.
The squad's original bug man, Keeler knew Navy experts whose eavesdropping systems did not require telltale wires.
World-class pool player and hustler, as "Freddie the Thief," he became an enterprising con man, but hoped for better for his son, Jack.
A dashing figure who played polo at an elite military academy, he eyed a Hollywood career but instead became "Jack the Enforcer."
He came from Cleveland to serve as a flunky for Cohen and told police "I'm the man" after Jack Whalen was shot.
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An original squad member, he took out-of-town hoodlums into the hills for "a little heart-to-heart talk," and became obsessed with proving Cohen a killer.
WILLIAM H. PARKER
A legendary disciplinarian and LAPD chief from 1950 to the mid-'60s.
Phelps gained a reputation as a bugging genius when he joined the squad in the 1950s and partnered with Jerry Wooters.
JOHN VON HURST
A grandson of Fred Whalen, he witnessed the visit of two men offering to help get revenge on Cohen.
A booster of the LAPD through the TV show "Dragnet," Webb turned to the Gangster Squad for help when going through a divorce.
Barely surviving World War II, Wooters joined the Gangster Squad and forged a secret alliance with Whalen.