In an interview with Entertainment Weekly, Cooper talks about Depp’s performance as Bulger in Black Mass. To re-create Bulger’s intimidating style and persona, Cooper and Depp pored over surveillance tapes and old FBI photographs. Cooper says of Bulger:
He could be charming. He could be ruthless. He was like a cobra – you never knew where he could strike…He murdered him in front of numerous witnesses in broad daylight. In a word, Whitey was brazen.
A lot of people on set knew Whitey intimately. They got chills at the resemblance. Some of them couldn’t even look at him… It’s easy to be the mustache twirling villain but this performance couldn’t be further from that. He is truly gifted.