At 0848 Central time, the two aircraft collided while preparing to land. The RV-6A was destroyed and its pilot fatally injured; the RV-8 substantially damaged; its pilot was not injured. Visual conditions prevailed. Both airplanes were part of a four-aircraft formation preparing to land at the time of the accident. The RV-8s pilot was the lead and reported the formation was established over the approach end of the runway when he initiated an overhead pattern. Shortly after starting his turn he felt the impact with the other airplane. He was able to maintain control and subsequently landed on runway 36. A ground-based witness reported the lead airplane executing a climbing left turn away from the other airplanes. Approximately two seconds later the second airplane began a left climbing turn. The witness reported that this airplane appeared to turn and climb much more aggressively than the lead aircraft. The second airplane then merged with the lead aircraft from below and from the left. The second airplane subsequently entered a near vertical, slow spiral descent in a nose-down attitude.