The reserve deputy who shot a suspect dead after firing his gun instead of his Taser was investigated in 2009 over his questionable training and erratic behavior in the field. Robert Bates, 73, appeared in Tulsa district court on Tuesday and pleaded not guilty to second-degree manslaughter over the death of Eric Harris, who was killed during a botched sting on April 2. Since the incident there have been allegations Bates was not properly trained and it is now emerged that when previously confronted by other deputies over his behavior, he told them he could do whatever he wanted. Scroll down for video . Heading to court: Robert Bates, left, is seen walking to court on Tuesday morning with his attorney Corbin Brewster, right, before he entered his not-guilty plea in the death of Eric Harris earlier this month . 'Mistake': The 73-year-old reserve deputy claims he mistakenly pulled out his gun instead of his Taser and shot dead the man as he fled the scene of an undercover operation on April 2 . In 2009, the Tulsa Sheriff's Office concluded after an internal investigation that Bates had received special treatment during training and while working as a reserve deputy, CBS News reports. The investigation found that other deputies raised concerns about Bates' behavior in the field, almost from the start of his tenure. He was said to have used his personal car while on duty and made unauthorized vehicle stops. The inquiry came to the conclusion that high-ranking officers created an atmosphere where employees were intimidated about reporting violations of department policy. Dan Smolen, the attorney for Eric Harris, claimed that if the investigation's findings had been acted on in 2009 Harris might still be alive. He told CBS News: 'I think there are so many people who look on at so much corruption it's more than just a couple of people.' Charged: Bates (left in his mug shot) shot Harris (pictured right) and faces four years in prison if convicted . A spokesman for the Tulsa Sheriff acknowledged that some type of internal review was conducted, but that there was no further action taken. Sheriff Stanley Glanz said this week he believes that Bates received his required training. Bates, a Tulsa County volunteer, shot Harris, 44, after the man was confronted during an undercover gun-sale operation and ran past him. Video of the incident shows Bates chasing after Harris. In an attempt to subdue him, Bates went to grab his Taser, but was unaware he had actually pulled out his gun instead. In the disturbing clip, which was released by the sheriff's office, Bates can be heard shouting 'Taser! Taser!' When the gunshot goes off, he says: 'I shot him! I'm sorry.' The fatally-wounded father can be heard saying: 'Oh my god, he shot me! He shot me! He shot me, man' before adding: 'Oh, my god. I'm losing my breath!' Earlier this week the Harris family expressed their anger after learning that retired insurance executive Bates, who is out on $25,000 bond, would be allowed to take a month-long vacation to the Bahamas. A statement released by the family read: 'Whether intended or not, Mr. Bates' vacationing in the Bahamas at this time sends a message of apathy with respect to the shooting and Eric's life,' they said. Shooting: This photo shows a deputy bending down to pick up Bates's dropped gun following the accidental shooting in Tulsa earlier this month. Harris is being held down on the ground, out of shot, by other deputies . Terrified: The fatally-wounded man, who is being held by his neck and back by the deputies (pictured), says: 'Oh my god, he shot me! He shot me! He shot me, man.' He then adds: 'Oh, my god. I'm losing my breath' 'At a time when we are still mourning the death of a loved one that he shot down in the street, Mr. Bates will be relaxing and enjoying his wealth and privilege.' It is not clear when he is leaving for the holiday but Bates will next appear in court on July 2. He has previously visited the Bahamas with the sheriff, Stanley Glanz, and another reserve deputy and paid for part of Glanz's trip. In separate news conferences on Monday, the county sheriff and lawyers for Harris' family disagreed on whether the reserve officer should have been allowed to conduct police work. Sheriff Stanley Glanz said Bates, his long-time insurance agent and former campaign manager, had been properly trained and passed annual firearms certifications required by the state. Dan Smolen, the lawyer for Harris' family, said the Tulsa County Sheriff's Office violated a number of its internal policies by letting Bates carry his personal handgun after training with another weapon. Smolen also said the department failed to keep a permanent record of Bates' training, in violation of local policies. Records Bates released during the weekend showed that the volunteer officer was trained on a .45, not the weapon used in Harris' death. Bates, who sold his insurance business for $6 million in 1999, was trained to be a Tulsa Police Department patrolman in 1964 but left in 1965. He was out of law enforcement for 35 years, returning for volunteer work in Florida in 2000 before joining the Tulsa County force in 2008 and making a number of donations to the agency. He also was Glanz's campaign manager during the 2012 election. Anger: Harris' son Aidan Fraley (pictured right with his uncle Andre Harris a week after his father's death), has said the police officers who allowed Bates to become a cop should be held accountable for his death . Confusion: An image shows a Taser and a handgun similar to the weapons Bates was carrying. He mistakenly thought he was holding a Taser, not his handgun, when he fatally shot Eric Harris . During an appearance on the Today show last week, he apologized to Harris' family. 'First and foremost let me apologize to the family of Eric Harris,' he said. 'I rate this as number one on my list of things in my life that I regret... I still can't believe it happened.' He also insisted that, despite keeping his gun and Taser on different parts of his uniform, it was easy to confuse the two. 'This has happened a number of times around the country, I have read about it in the past,' Bates said. 'I thought to myself after reading several cases, 'I don't understand how this can happen'. You must believe me - it can happen to anyone.' Harris' son responded by saying that the volunteer deputy was too old to be on the police force. 'He should have been in a retirement home, not out there on the scene killing my dad,' Aidan Fraley said, NBC reported. During an appearance on the Today show last week, Bates apologized to Harris' family .
Tulsa reserve deputy Robert Bates investigated in 2009 over his behavior .
Concluded that he got special treatment and received questionable training .
He has pleaded not guilty to manslaughter over death of Eric Harris, 44 .
73-year-old killed the father after drawing gun instead of Taser during sting .