During the landing flare, the pilot realized the landing gear had not been extended when the “step” contacted the runway. He initiated a go-around; however, the airplane did not climb as expected. The pilot attempt to land on a different runway and extended the landing gear but the airplane descended rapidly and impacted terrain. The left main and nose landing gears collapsed. A post-impact examination revealed the propeller had impacted the runway during the first landing attempt. The pilot reported that there were no mechanical malfunctions prior to the accident.