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Robert Bates, the 73-year-old reserve sheriff's deputy who shot and killed an unarmed man last year in Tulsa, Oklahoma, was convicted Wednesday of second-degree manslaughter.

Jurors recommended that Bates, who is now 74, serve the maximum sentence of four years in prison, NBC station KJRH reported.

Bates, a retired insurance executive who moonlighted as a volunteer on a violent crimes task force, shot Eric Courtney Harris, 44, on April 2, 2015, after Harris ran from Tulsa County sheriff's officials who'd caught him in a gun-sale sting.

Bates said he thought he was reaching for his Taser when he shot Harris, who suffered a fatal gunshot to his left armpit. In a video of the encounter, Bates can be heard shouting, "Taser! Taser!" and later saying, "I shot him! I'm sorry!"

The shooting of Harris, who was black, inserted Tulsa into the national debate over police attitudes toward black people. It also led to the indictment and resignation of Sheriff Stanley Glanz, Bates' longtime friend, for allowing a non-officer to take part in a violent law enforcement operation.

Related: Tulsa County Sheriff Indicted, Resigns in Wake of Fatal Shooting by Deputy

Bates told TODAY last year that accusations that he wasn't properly trained and was allowed to "play cop" were "unbelievably unfair." He said that when he heard the gunshot, he thought, "Oh, my God, what has happened?"