Black Mass cast and crew on their approach to real-life gangsters

In their own ways, gangster James “Whitey” Bulger and his politician brother, William M. Bulger, both traded in power and influence. As one of the latter’s rivals once said, “What Whitey does with a gun, Billy does with a gavel.”

That dichotomy was part of what attracted filmmaker Scott Cooper to their story in Black Mass, the big-screen crime drama starring Johnny Depp as Whitey and Benedict Cumberbatch as Billy.

“Here you have this man who was the most powerful and notorious gangster in Boston’s history, while his brother was the most powerful politician in the city of Boston,” Cooper told EW during the recent Toronto International Film Festival. “Then you add in the fact that their childhood friend, John Connolly, was ascending the ranks of the FBI, and of course allowed Whitey to operate with impunity and essentially giving him a license to kill. You just can’t make this stuff up.”

Completing the unholy trinity of Black Mass is Joel Edgerton, who portrays Connolly in the film. For his performance, he was informed by an observation that one of Connolly’s old colleagues had made about him.

“This FBI agent had said of John that he was a real peacock, and he really kind of strutted around the FBI office,” Edgerton said. “I thought that was good information for me, and tried not to take that too far in a caricatured way, that John started to develop a bit of a strut. That he was sort of strutting his way into being a gangster.”

For more from Cooper and Edgerton, watch the full clip above.

Black Mass is in theaters now.