Reginald Mitchell pleaded guilty Thursday in Miami federal court to robbery conspiracy, interfering with commerce and possession of a firearm resulting in death during a crime of violence.
Authorities say the 27-year-old man is one of several people who plotted to rob a Brinks truck at Calder in August 2011.
Mitchell's girlfriend, 27-year-old Victoria Barkley, has also pleaded guilty for her role, and 24-year-old Byron Kyler is scheduled for a change of plea hearing later this month.
Authorities say 34-year-old Vladimir Louissant fired the shot that killed Alvaro Lopez Ramos.
He and 27-year-old Uri Ammar, who had worked as a security supervisor at the track, are still awaiting trial.