According to the Oklahoma State Bureau of Investigation, at least 1,500 people were in attendance at the annual Memorial Day outdoor festival in the Old City Square.
Witnesses told police that an argument started just after midnight and shots were fired.
In total, eight people were shot, authorities say. One person has died and seven others were injured, including two juveniles.
The Muskogee County Sheriff’s Office had deputies at the event already and immediately rendered aid to the victims, according to the Oklahoma State Bureau of Investigation.
As of Sunday afternoon, there were no suspects in custody. Anyone who attended the event and witnessed the shooting is urged to contact the OSBI at (800) 522-8017 or email email@example.com. The agency says you can remain anonymous.