Puka Nacua's brother, Samson Nacua, has more than just the UFL investigation to worry about after he slapped a fan at Saturday's game -- St. Louis Police tell TMZ Sports they are currently looking into the matter.
A spokesperson says the department is aware of the video from the St. Louis Battlehawks game on Saturday ... which shows Samson, who plays for the Michigan Panthers, slapping a fan at The Dome at America's Center.
"We are conducting a thorough investigation into the incident and we are working to obtain video from The Dome at America's Center that may have captured what led up to the encounter," the St.