A white volunteer deputy sheriff in the US state of Oklahoma has been charged with manslaughter for the fatal shooting of an unarmed black man that was recorded on video.

Tulsa County prosecutors filed a second-degree manslaughter charge against 73-year-old Robert Bates, the latest shooting of an African-American by a white police officer to draw scrutiny.

Police treatment of minorities has become a major issue in the US after the killings of unarmed black men in Ferguson, Missouri, New York City and recently South Carolina.

A police investigator has said Bates thought he drew a stun gun, not his handgun, when he fired at 44-year-old Eric Harris in the April 2 shooting.

Bates is charged with second-degree manslaughter "involving culpable negligence," Tulsa County District Attorney Steve Kunzweiler said in a statement.

Oklahoma law defines culpable negligence 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," Kunzweiler said.

Video footage released

A video of the incident shot by deputies with sunglass cameras and released at the request of the victim's family, shows a deputy chase and tackle Harris, whom they said tried to sell an illegal gun to an undercover officer.

As the deputy subdues Harris on the ground, a gunshot rings out and a man says: "Oh, I shot him. I'm sorry."

Harris was treated by medics at the scene and died in a Tulsa hospital.

Bates, an insurance broker in Tulsa who contributed to the Tulsa County sheriff's re-election campaign, has publicly acknowledged shooting Harris, a one-time convict who was tackled while fleeing an undercover gun sale sting operation.

The Tulsa World newspaper reported that he is among several Tulsa residents who moonlight as reserve deputies.