On September 12, 2006, about 0855 Pacific daylight time, a Cessna U206G, N6238U, departed the parking area, independent of pilot control, before taxiing through a fence, hitting a street sign, and coming to rest on an embankment 75 yards from Wasco-Kern County Airport (L19), Wasco, California. The airplane was owned by Inland Crop Dusters, Inc., Shafter, California, and operated under contract by the Integrated Pest Control Branch of the California Department of Food and Agriculture (CDFA) as a public-use operation for agricultural application. The commercial pilot, the sole occupant, was not injured; the airplane sustained substantial damage. Visual meteorological conditions prevailed, and no flight plan had been filed. The National Transportation Safety Board investigator interviewed the pilot. The pilot reported that the purpose of the flight was to distribute sterile pink bollworm moths on multiple cotton fields in the local area. The pilot reported that he needed to use the restroom and decided to land at Wasco to use the facility at the airport. The pilot stated that he parked the airplane about 50 feet from the restroom facility, set the engine power at idle, activated the parking brake, and departed the airplane. While in the restroom, he heard a change in the engine sound and heard a distinct "click" of the parking brake disengage, and came out to see the airplane moving. He heard the engine rpm increase from idle to about 1,200-1,500 rpm, and watched as the airplane "sped" away, about 30 mph. As he chased after the airplane, he watched as the airplane hit a bump, turned 120 degrees to the left, went down the ramp at the end of the field, through the airport perimeter fence, hit a street sign, went over two roads, and came to rest on an almond orchard embankment. The airplane sustained structural damage to the left wing strut and leading edges of both wings. In the pilot's written submission, he wrote that stopping the engine prior to leaving the controls was how the accident could have been prevented.