A former Oklahoma volunteer sheriff's deputy who fatally shot an unarmed man faces arraigned on a second-degree manslaughter charge.

Former Tulsa County Sheriff's Office reserve deputy Robert Bates is scheduled to appear Monday in Tulsa district court.

Bates has pleaded not guilty in the April 2 shooting death of Eric Harris, saying he confused his stun gun and handgun.

After the shooting and a leaked memo from 2009 that raised concerns about Bates' training, a judge ordered a grand jury to investigate whether reserve deputies who gave donations to the sheriff have been given special treatment. Thousands of residents signed a petition to empanel the grand jury, which convenes July 20.

Bates donated thousands of dollars in cash and equipment to the agency and was the sheriff's campaign manager.