Abstract: The employer was tripping and removing the 4.5-inch drill string from the well bore. The employer had already removed ten stands of 4.5-inch drill pipe from the well bore and had placed the bottom of the drill pipe on the wooden drill rig floor with the upper part secured in the fingers of the pipe racking board. In this case, a stand of drill pipe consisted of two sections of 4.5-inch drill pipe which were each approximately thirty feet in length and weighed 16.60 pounds per foot. The ten stands of 4.5-inch drill pipe were racked on the east side of the drill rig floor. The employer was in the process of removing the eleventh stand of 4.5-inch drill pipe when the derrick mast suddenly and without warning collapsed. The derrickman apparently rode the derrick down, due to the fact that even though the Geronimo Emergency Escape Device was installed on the Geronimo Emergency Escape Line, there was not time to disconnect from the lanyard hook and to access the Geronimo Emergency Escape Device. The top section of the derrick mast collapsed to the west side of the rig floor, with the crown resting on top of the caliche at ground level. Employee #1 was asphyxiated and Employee #2 suffered fatal fractures. Employee #3, Employee #4, Employee #5 and Employee #6 were hospitalized.