OMAHA, Neb. (AP) — A state criminal prosecutor will lead a grand jury investigation into Omaha police officers’ actions in the stun gun-related death of a mentally ill man.

Corey O’Brien, head of the criminal division of the Nebraska Attorney General’s Office, will lead the grand jury investigation into the June 5 death of 29-year-old Zachary Bearheels.

Last month, a judge ruled that Douglas County Attorney Don Kleine could not lead the investigation, citing Kleine’s announcement in July of charges against former officers Scotty Payne and Ryan McClarty separate from the grand jury process.

Police video shows Payne using a stun gun repeatedly on Bearheels, and McClarty is seen punching Bearheels. Some of the blows came after Bearheels was on the ground and not resisting.

Payne has been charged with felony assault. McClarty is charged with misdemeanor assault.

Nebraska law requires a grand jury probe when someone dies in police custody.