A 5,000-pound steel beam was stacked on a rack. As the rigging was released and the crane pulled the chain away from the load, it swung and struck/caught the beam. The beam and rack then began to roll toward an employee. The beam fell from the rollers and struck the employee, resulting in a right leg amputation at the mid-calf and a left leg amputation above the knee. Another employee was also injured but was not hospitalized.