A 73-year-old reserve deputy shot and killed a man during an undercover operation after thinking he had his stun gun when he opened fire. Robert Charles Bates shot and killed Eric Courtney Harris as the younger man was trying to buy drugs and a gun from deputies posing as dealers in the parking lot of a dollar store. Harris, 44, was being restrained by one of the undercover police officers when Bates, who was monitoring from afar, ran up 'trying to get the situation under control' and fired one shot. According to police at the scene in Tulsa, Oklahoma, Bates, a former full-time officer, accidentally pulled out his service weapon instead of the stun gun. Confusion: Robert Charles Bates, 73, accidentally grabbed his pistol and shot a man dead, it has been claimed . Major Shannon Clark told CNN: 'They were struggling trying to get him into custody, he ran up trying to use a less lethal device, trying to get the situation under control, inadvertently he discharged a round from his service weapon.' He added: 'Did an accident happen? Sure. But is it accredited to his age? Or was it accredited to the rapidly evolving situation? I guess that will be determined in the investigation.' Bates, who has been a reserve since 2008, is the chief executive of Robert C Bates LLC, a Tulsa-based insurance company, who worked as an officer assigned to the Violent Crimes Task Force. He also spent time with the Tulsa Police Auxiliary. Speaking to local site News OK, Bates said: 'It was me. My attorney has advised me not to comment. As much as I would like to, I can’t.' According to Tulsa Police, Harris had met an undercover officer to sell him a 9 mm semi-automatic pistol and 300 rounds ammunition and ran when deputies tried to arrest him, then fought with another deputy when he was shot. Killed: Eric Harris, 44, was allegedly meeting with undercover deputies to buy a 9 mm semi-automatic pistol . He was gunned down after officers 'observed him reaching for his waistband area ... causing concern for the deputies' safety,' CNN reported. Officers had been monitoring Harris as part of an investigation into the trade of methamphetamine. As he met with undercover deputies to allegedly hand over the drugs, he is accused of offering to throw in a sawed-off gun. His convictions include escaping prison in 1990, robbery with a dangerous weapon in 1999, and making threatening phone calls. According to Tulsa Police, Harris' killer, Bates, is classified as an advanced deputy. Reserves are 'basic', 'intermediate', or 'advanced'. The qualify for 'advanced', officers are required to have a minimum of 320 hours of training and 25 hours of training a year. During the annual field training program, they are tested on how to use and identify lethal and non-lethal weapons. With the same power as paid deputies, reserves can conduct their own investigations, make arrests and work on task forces.
Robert Charles Bates, 73, was allegedly trying to pull out his taser .
He killed 44-year-old Eric Harris, who was 'buying' a gun from undercovers .
Police in Tulsa, Oklahoma, said Harris may have had a gun on him .
The victim was being restrained by an undercover officer when Bates ran up .