The shooting left another man with a gunshot wound to his leg, according to KCNC-TV. His injury did not appear to be life-threatening.
A spokesperson for the Denver Police Department described the shooting to KMGH as "an unintended discharge" of the off-duty agent's weapon. It was not immediately clear whether the agent was drinking at the time of the incident, KCNC-TV reported.
Police told KMGH that the agent was taken to Denver police headquarters after the shooting and released to an FBI supervisor.
Police are investigating the incident. The Denver District Attorney's Office will determine whether the off-duty FBI agent will face charges for the incident, The Washington Post reported.