Yep, totally and utterly self-inflicted.
Terrance Yeakey was discovered dead in a field near his hometown, El Reno, a mile and a half (2.4 km) away from his abandoned, blood-soaked car parked on the country road.
Yeakey was mutilated and shot to death: slit at his wrists, arms, elbows, stabbed in both sides of his neck near the jugular vein and shot in the side of the head at a 45-degree angle with a small caliber revolver. Signs of hauling, such as rope burns on the neck, handcuff bruises to the wrists, muddy grass embedded in the wounds were observed on the body. No evidence of alcohol was found in Yeakey's body.
According to anonymous officers, no weapon was found at the scene despite the in-depth official investigation, until an FBI helicopter arrived.