At approximately 1415 Mountain time, the airplane was substantially damaged when it nosed over during a forced landing. The Commercial pilot and a passenger were not injured; visual conditions prevailed. According to the pilot, the engine began running rough, then lost all power. He made a forced landing in an open field. During the landing roll the airplane nosed over, crushing the vertical stabilizer and the top of the upper wing. He said that fuel leaking from the fuel tanks after the accident smelled like kerosene.