John Connolly grew up in the South Boston housing projects a few doors down from the Bulger family. He formed a fast friendship with Billy Bulger, and admired Billy's mysterious and mischievious older brother, "Whitey." By the mid-1970s, Connolly was an up-and-coming FBI agent eager to make his mark in the agency's Boston office. Bulger, meanwhile, was climbing the ranks of the city's underworld and looking to expand his power. In 1975, the old Southie acquaintances formed a partnership from which both would benefit.

Connolly persuaded Bulger to sign on as an informant, a coup that soon made Connolly a star within the FBI. The agency valued high-level snitches, and in the Boston office there were none more highly placed than "Whitey" Bulger. Working on tips from Bulger and his partner, Stephen Flemmi, the FBI began dismantling the Irish mob's chief rivals, the Italian Mafia, paving the way for Bulger's ascendancy.

In exchange for the valuable tips Bulger provided, Connolly and his fellow agents allegedly helped the gangster elude the law by tipping him off to sting operations and cutting deals to save him from prosecution. Under this cloak of protection, Flemmi and Bulger built a blood-stained drug and racketeering empire.

Connolly retired from the FBI in 1990, accepting a highly paid job with Boston Edison and eventually retiring in 1991. With Connolly out of the picture, the FBI dropped Bulger and Flemmi as informants and began targeting them, eventually handing down federal racketeering and extortion charges against the pair in 1995.

The dark details of the FBI's secret pact with the Mob emerged in 1998, during a year-long series of federal court hearings into Flemmi's request to dismiss racketeering charges against him. The following year, a federal indictment charged Connolly with alerting Bulger and Flemmi to investigations, falsifying reports to hide their crimes, accepting bribes, and funneling payoffs to his former supervisor, John Morris. A second indictment handed down in 2000 charged the former FBI star with leaking information to Bulger and Flemmi that led to three slayings.

This profile was written by the staff of Boston.com based on material from The Boston Globe archives.