Abstract: On November 17, 2009, four employees from Cactus Drilling Co. LLC, were conducting modifications to an oil/gas well drilling rig. Before a fifth employee left the job site, he identified the required rig components that needed to be changed. The parts, including the mast"a"legs, weighed approximately 56,000 pounds when assembled. Stallion Oilfield Services, a Cactus Drilling Co. Sub-Contractor, had six contractor coworkers on site to provide lifting and hauling services as well as vehicles and equipment. Two contractor coworkers left after the substructure was complete and the mast section was removed from the tandem truck. The Stallion crane was to lift then swing the starter section with the attached "a" legs into the riggers beam. Employee #1 and Employee #2 pinned the "a" legs into their respective shoes. Coworker #1 was directing the crane, and Coworker #2 was directing the gin pole truck and forklift. Employee #3, a tool pusher, was standing on the ground next to the crane cab. Employee #4 was operating the forklift. Coworker #3 was operating the 275 ton hydraulic crane and Coworker #4 was operating the gin pole truck. Employee #3 directed the crane and lifted and swung the assembly nearly to the break over point getting the mast section nearly erect; however, the crane could not swing any further. He made multiple attempts but failed to complete erecting the mast section and securing the "a" legs into position. Coworker #3 and his flagger were trying to figure out what was keeping the crane from swinging the mast section and "a" legs into position. At this time, the crane attachment point and the "a" legs spreader beam failed. It broke into four pieces. The center section, approximately 6 ft long, attached to the crane line flew up and then fell to the floor, striking Employee #1 and Employee #2. Employee #1 was killed and Employee #2 was severely injured (injuries were not specified). Employee #2 was airlifted to a hospital, where he later died from his injuries. The investigation is on-going.