The Oklahoma State Bureau of Investigation announced on Monday that it is opening a formal inquiry into the sheriff’s office that oversaw Robert C. Bates, the 73-year-old reserve deputy who shot and killed Eric Harris in April, the Associated Press reports.

Since the shooting, the Tulsa County Sheriff’s Office has been accused of misconduct over the supervision of Bates, who claims he meant to fire his Taser at Harris and inadvertently drew his gun. From NBC News:

NBC News reported last month that a 2009 report revealed that Bates, a longtime friend and political supporter of Sheriff Stanley Glanz, got preferential treatment at the sheriff’s office and didn’t complete certain training required of other deputy sheriffs.

The report found that two senior sheriff’s officials, Undersheriff Tim Albin and Maj. Tom Huckeby, fostered a culture of intimidation if other employees raised concerns about Bates’ lack of training hours or skill.

Last month, Tulsa County District Attorney Steve Kunzweiler said the 2009 report raised concerns about the sheriff’s office “beyond the scope” of the Harris shooting and requested an investigation from Oklahoma’s Attorney General.

In their announcement today, the OSBI said a special prosecutor will be given a thorough report once the investigation is completed and will decide if the sheriff’s office broke the law.

[Image via AP Images]