(CNN) -- The Tulsa County deputy who shot and killed a man instead of using his Taser now faces a manslaughter charge.
Video shows Reserve Deputy Robert Bates announcing he is going to deploy his Taser after an undercover weapons sting on April 2, but then shooting Eric Courtney Harris in the back with a handgun.
In a written statement, Tulsa County District Attorney Stephen A. Kunzweiler said Bates is charged with second-degree manslaughter involving culpable negligence, defined by Oklahoma law 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."
Investigators' efforts to defend Bates and the other deputies involved in the arrest have sparked a mounting chorus of criticism online.
Authorities say Bates thought he pulled out his Taser but "inadvertently" fired his gun. They've painted Harris as a dangerous, possibly PCP-addled illegal gun dealer who had recently sold methamphetamine to undercover police and who fled police that day in such a way as to give the impression that he had a gun in his waistband.
Though Harris was later determined to be unarmed, Sgt. Jim Clark of the Tulsa Police Department, who has been brought in to review the case, excused the behavior of Bates and the officer who is heard cursing at Harris.
Clark said Bates, who was also one of the benefactors of the Tulsa County Sheriff's Office, was the "victim" of something called "slip and capture," where in a high-stress situation, a person intends to do one thing and instead does something else.
Andre Harris told reporters Monday that claims his brother was violent and on PCP are false.
"He was nonviolent, he was peaceful, he was loving, he was caring, and he was my brother that I'll never see again 'til I see him in heaven," Harris told reporters, accusing authorities of trying to persuade him not to hire an attorney.