The number of possible killers grew and grew, as investigators probed their underworld connections and bargained with convicts who were willing to dish the dirt in exchange for a reduction in their sentences.
Between January 1976 and February 1977 the United States government issued internal reports which were based on interviews with an informer who claimed to know the entire story of Hoffa's disappearance. The informer, Ralph Picardo was serving a sentence for murder at Trenton State Prison in New Jersey. In 1975 Picardo was a driver for 'Tony Pro' Provenzano and he revealed that Hoffa had been invited to the restaurant meeting by renowned Detoriot mobster, Anthony Giacalone for a 'sit down' with Provenzano to make amends over their differences.
O'Brien, who claimed to have been on a fish-carving expedition that day, had, according to Picardo, picked up Hoffa at the restaurant and driven him to a nearby house where Teamster business agent Thomas Andretta, Salvatore Briguglio and his brother Gabriel waited to ambush Hoffa. Frank Sheeran was also present.
Picardo claimed that the hit had been ordered by Pennsylvania mob boss Russell Bufalino, because his cousin, William, had a big falling out with Hoffa in 1967, and Bufalino had passed the actual deed of murder onto Provenzano.
Bufalino's exact whereabouts on the day Hoffa was murdered were never confirmed but the FBI believed there was little doubt that Hoffa was murdered, as Picardo had confessed.
In 1985 the FBI released a memo summarising citing, Briguglio along with brother Gabriel, Andretta, O'Brien, Provenzano, Giacalone and Bufalino as their prime suspect for Hoffa's murder.