While in prison, Richard Kuklinski claimed to be responsible along with four other men for the kidnap and murder of former Teamsters union boss Jimmy Hoffa on July 30 1975 in a restaurant parking lot in Detroit. The five-man team were allegedly given the contract on Hoffa by Tony Provenzano, a captain in the Genovese crime family. Kuklinski claimed to have been paid $40,000 for the hit. Kuklinski said that he knocked Hoffa unconscious with a blackjack and, while holding Hoffa's chin up, thrust a hunting knife into the back of his head. Hoffa's body was then allegedly placed in the trunk of a car that was then crushed and sold as scrap metal to Japanese car makers. The claims only surfaced after Kuklinski's death in March 2006 in a book by author Philip Carlo and will probably never be substantiated.
Apart from a 15 second flashback, the film makes virtually no mention of the awful childhood that Richard Kuklinski endured. His parents were both deeply violent people, with his father actually accidentally beating his older brother to death. In real life, this played out into Kuklinski becoming a very violent person himself. The film completely glosses over the fact that he regularly beat his own wife.
Before production began, director Ariel Vromen shot a test scene with Michael Shannon as Richard Kuklinski and Michael Wincott as Robert Pronge. Shannon kept his role in the feature version, while Chris Evans was cast as Robert Pronge because Vromen wanted someone younger for that part. The director offered Wincott another role, but the actor wasn't happy with it and amicably refused.