Authorities say an Oklahoma reserve deputy who shot and killed a man during an undercover operation thought he had his stun gun when he opened fire.

The Tulsa County sheriff's office told reporters Friday that 73-year-old reserve deputy Robert Charles Bates shot and killed Eric Courtney Harris after pulling out his service weapon instead of the stun gun.

Bates is an insurance company executive assigned to the Violent Crimes Task Force. The sheriff's office said Bates spent time with the Tulsa Police Auxiliary and is a former full-time officer.

Maj. Shannon Clark said Harris had met an undercover officer to sell him a pistol and ammunition and ran when deputies tried to arrest him, then fought with another deputy when he was shot.