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A Tulsa, Oklahoma reserve sheriff's deputy was charged with second-degree manslaughter Monday for the shooting death of an unarmed black man.

The charges against Robert Charles Bates came hours after the family of the dead man, Eric Courtney Harris, accused deputies of treating him inhumanely after he was shot at the conclusion of an April 2 foot chase stemming from a sting operation in which Harris had allegedly arranged to sell a gun to undercover officers from the Tulsa County Sheriff's Office Violent Crimes Task Force.

Video footage of the incident showed Harris writhing on the ground and complaining that he was having trouble breathing. An unidentified officer can be heard responding, "F--k your breath."

Harris' family released a statement Monday calling the response "appalling." The relatives added, "No human being deserves to be treated with such contempt."

Bates, 73, an insurance agent who'd served as a reserve deputy since 2008, thought he was using a Taser on Harris, but shot him with a gun instead, sheriff's office investigators have said.

In the video, Bates can be heard shouting, "Taser! Taser!" before firing a single round from his sidearm, hitting Harris, who was pinned to the ground by officers.

Bates quickly realized his mistake: "I shot him! I'm sorry!" he is heard saying.

Harris was taken to the hospital, where he died about an hour later.

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The Tulsa County Sheriff's Office defended Bates last week, saying he committed no crime, noting that officers chasing Harris had good reason to fear that he was armed. They said Harris, a felon, had a history of violence against police officers and had placed his hand near his waistband during the chase. Tulsa Police Sgt. Jim Clarke, who reviewed the incident for the sheriff's office, called the shooting an accident attributable to a faulty response to stressful situations called "slip and capture."

They then turned the investigation over to Tulsa County District Attorney Stephen Kunzweiler, who on Monday announced the second-degree manslaughter charges.

Underpinning the charge is a finding of what Kunzweiler called in a statement "culpable negligence," which Kunzweiler defined as "the omission to do something which a reasonably careful person would do, or the lack of the usual ordinary care and caution in the performance of an act usually and ordinarily exercised by a person under similar circumstances and conditions."

Attorneys representing the Harris family said Monday evening that they had evidence that the sheriff's office had misled the public about the incident, and promised to release it, piece by piece, in coming weeks.

"This horrible situation is going to be about what a corrupt sheriff’s office does after a bad shooting," one of the lawyers, Daniel Smolen, said.

Harris' family accused Clarke and the sheriff's department of seeking to protect Bates, who, according to the Tulsa World newspaper was a chairman of Sheriff Stanley Glanz's 2012 re-election campaign, to which he donated $2,500. The paper, citing Tulsa County records, also said Bates donated several cars to the undercover unit.

In an interview with the paper, Glanz said he had been friends with Bates for about 50 years, and that Bates had been his insurance agent. But Glanz said he had not given Bates preferential treatment.

It is common practice for supporters to be hired as reserve deputies, who undergo police training and are assigned to accompany sworn officers on law enforcement operations, Glanz has said. Clarke's report noted also that Glanz had more than 400 hours of training since 2007.

Harris' family questioned the wisdom of having a 73-year-old insurance executive, who'd served briefly as a police officer in the 1960s, involved in a undercover sting operation, let alone someone who'd given political donations to his boss.

"We do believe something is deeply wrong with the Tulsa County Sheriff's Office," the family statement said.

Such arrangements are not unheard of, in Oklahoma or elsewhere. In Michigan, for example, some small town police departments, strapped for cash, have hired volunteer cops to help fight crime. Sometimes the hires pay for their uniform and gun.

"In this state and many others, you have to have a license to practice law, to practice medicine, to cut hair and do nails, yet this subsection of my industry exists almost unchecked," said Dave LaMontaine, president of the Deputy Sheriffs Association of Michigan.

He added, "In some places, it's pay to play."

The hiring of volunteer reserve sheriff's officers dates back to the days of the Wild West, when sheriffs sought help from citizens enforcing the law, experts said.

In the modern versions, reserves must complete some sort of training, depending on the state and agency where they work. In some states, reserves can carry guns, and additional training earns them the ability to work closely with police officers. Certain categories of California deputies can patrol areas on their own, Police Foundation President Jim Bueermann said.

Jonathan Thompson, deputy executive director of the National Sheriffs' Association, said the hiring of reserve officers has increased since 9/11, with fears of terror attacks that could strain local departments. With a generation of baby-boomer officers retiring, there is a large pool of former officers to recruit from, he said.