The FBI is investigating the killing of a tribal police officer in southern Arizona. A Tohono O’odham police officer was killed Thursday near the Desert Diamond Casino south of Ajo.

An FBI spokeswoman said a suspect was being treated for injuries at a hospital.

Border Patrol Sector Chief in Tucson Roy Villareal said in a statement that a Border Patrol agent assisted tribal officers and that agents later apprehended the man. The Border Patrol’s Office of Professional Responsibility is also investigating the incident.

The killed officer has not yet been identified.