On June 14, 1994, at 1130 central daylight time, a Grumman G-164D, N164MC, was destroyed while maneuvering near Gilbert, Louisiana. The commercial pilot was fatally injured, while his passenger sustained serious injuries. Visual meteorological conditions prevailed for the positioning flight. According to the property owner, the pilot was forced to terminate his agricultural spraying work due to high winds in the area. He added that the pilot had asked his flag man to ride back to home base with him to assist in getting the airplane changed over from liquid to dry spraying. The pilot removed a large inspection panel aft of the pilot's seat so the flag man could ride standing up unrestrained. Witnesses observed the airplane enter a flat spin after the airplane became inverted while attempting to perform a slow roll at an estimated altitude between 1,200 and 1,400 feet AGL. The airplane came to rest on a rice field. The engine was found buried in the soft ground, with a 6 inch portion of a propeller blade tip above the ground. The surviving passenger did not make himself available for an interview, nor will he complete a passenger statement form sent to his residence.