Santiago Gonzalez, 49, of Davie had been convicted of attempted drug trafficking and a weapons offence but was not charged in the killings, the South Florida Sun Sentinel reported Tuesday.
The 1995 murders of Frank Griga and Kristzina Furton are the subjects of the movie "Pain and Gain" starring Mark Wahlberg and Dwayne "The Rock" Johnson that was released two weeks ago.
Santiago had been an armed escort for a man he thought was smuggling 67 pounds of cocaine, but who actually was an undercover agent with Alcohol, Tobacco and Firearms.
While acting as an armed escort, Santiago was recorded saying he had guarded marijuana shipments in the past and offered to provide "armed protection services" for $250 a pound.
Gail Levine, an assistant state attorney who prosecuted three men in the beheadings, said she had "no credible evidence" that linked Gonzalez to the slayings.
Two of the three men convicted for their roles in the murders are on death row.