Chase Bishop, 29, was being held in a detention center in downtown Denver. It's unclear whether he has an attorney.
Bishop was partying at Mile High Spirits, a distillery and dance club in the Ballpark neighborhood, while off duty. In the video, Bishop is dancing and then performs a back flip.
As he picks up the gun from the floor, it fires.
Federal Bureau of Investigation officials have refused to release Bishop's name although he had been identified by other media outlets. This agent also said that if there are aggravating circumstances to the accidental discharge, the discipline could be more severe, up to termination.
Bishop is not assigned to the Denver office but works out of Washington, sources told KUSA.
"We sat down at one of those picnic tables - I heard a loud bang and I thought some idiot set off a firecracker", Reddington told ABC News later.
"Then I looked down at my leg and see some brown residue, ..."
The FBI declined to comment on the matter on Tuesday (local time) "in order to preserve the integrity of the ongoing investigation", spokeswoman Amy Sanders said.
The video shows the off-duty agent reaching for the gun and allegedly accidentally firing the weapon, hitting another patron in the leg.
Bishop turned himself in to the Denver Sheriff Department on Tuesday morning after a warrant was issued for his arrest, according to Denver police. "I'm still thinking it's a firework. all of a sudden from the knee down my leg became completely red", Reddington, 24, said.
Colorado gun laws allow "qualified current and retired law enforcement officers" to carry concealed handguns. She previously covered criminal justice, courts and legal affairs at the Indianapolis Star.