At 1305 Pacific time, the airplane made a hard right turn while in the landing flare and impacted terrain. The Private pilot and one passenger were fatally injured; the other passenger was seriously injured. The airplane was destroyed. Visual conditions prevailed. Witnesses reported that they observed the airplane make a normal landing approach and flare. The engine suddenly went to full power, the nose pitched up and then the plane abruptly turned to the right. It then rolled to the right and impacted the ground inverted.