Benedict Cumberbatch has signed on to replace Guy Pearce in Warner Bros.' Whitey Bulger biopic Black Mass.

Guy Pearce signed on to play Whitey Bulger's brother Billy, the former President of the Massachusetts State Senate, back in March, but The Boston Globe reports that Benedict Cumberbatch has now taken over the role, although it isn't known why the casting switch was made. Shooting is currently under way in Boston. Billy was never implicated in Whitey's criminal activities, but his political opponents often tried to use his brother's reputation against him.

In related news, The Hollywood Reporter has word that Adam Scott has signed on to play FBI agent Robert Fitzpatrick.

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Johnny Depp is playing Whitey Bulger, with Joel Edgerton playing his longtime friend and FBI agent John Connolly, who helped Whitey get rid of his criminal competition in Boston. After getting tipped off that the government was about to double-cross him, Whitey Bulger went into hiding for several years, before he was apprehended in Santa Monica, California in 2011. He is currently serving two consecutive life sentences in federal prison. The criminal served as the inspiration for Jack Nicholson's Frank Costello in 2006 Best Picture winner The Departed and Pete Postlethwaite's Fergus "Fergie" Colm in The Town.

Scott Cooper is directing from an adapted screenplay by Mark Mallouk and Jez Butterworth, based on the book Black Mass: The True Story Of An Unholy Alliance Between The FBI And The Irish Mob by Dick Lehr and Gerard O'Neil.