Black mass: Whitey Bulger, the FBI, and a devil's deal

When the FBI turned an Irish mobster into an informant, they corrupted the entire judicial system and sanctioned the worst crime spree Boston has ever seen. This is the true story behind the major motion picture.
James "Whitey" Bulger became one of the most ruthless gangsters in US history, and all because of an unholy deal he made with a childhood friend. John Connolly a rising star in the Boston FBI office, offered Bulger protection in return for helping the Feds eliminate Boston's Italian mafia. But no one offered Boston protection from Whitey Bulger, who, in a blizzard of gangland killings, took over the city's drug trade. Whitey's deal with Connolly's FBI spiraled out of control to become the biggest informant scandal in FBI history.
Black Mass is a New York Times and Boston Globe bestseller, written by two former reporters who were on the case from the beginning. It is an epic story of violence, double-cross, and corruption at the center of which are the black hearts of two old friends whose lives unfolded in the darkness of permanent midnight.