Abstract: On September 19, 2002, Employee #1, a welder, and Employee #2 were replacing the threaded studs from an air dump piston cylinder on a bottom drop railroad car. They removed the cylinder by torching off the bolts. They wiped the grease off the top of piston and were welding nuts onto the broken-off studs to screw them off. One stud was already out when they started to attach the nut to the first stud. Employee #1 was welding and Employee #2 was holding the nut in place when the cylinder pistons, driven by internal combustion, activated and struck both workers. Employee #1 sustained facial injuries, for which he was hospitalized. Employee #2 was struck in the face and chest, and was killed.