TULSA, Okla. (AP) -

A former federal prosecutor says prosecutors in Tulsa were right to swiftly charge a white police officer with first-degree manslaughter in the fatal shooting of an unarmed black man.

Chicago-based defense attorney Phil Turner says prosecutors "must have thought charges were warranted and we can always upgrade the charge later."

Tulsa County District Attorney Steve Kunzweiler filed a first-degree manslaughter charge Thursday against officer Betty Shelby, who shot and killed 40-year-old Terence Crutcher on September 16 after she was responding to an unrelated call and came across Terence Crutcher's vehicle abandoned in the middle of a north Tulsa street. Video released by police showed Crutcher walking away from Shelby with his arms in the air.

Turner says prosecutors may have been motivated to move quickly in part to allay outrage and avoid the kind of street protests that have happened in Charlotte, North Carolina.

Police there have refused under mounting pressure to release video for the shooting of another black man this week. The National Guard has been called in to try to head off a third night of violence.