Abstract: Employee #1 and his coworkers on an oil well servicing crew had completed replacing a well's pump and reassembling of its pumping unit when the unit's electrical power source was interrupted. This rendered the unit inoperative and required the use of the service rig to simulate the unit's movement in testing the pump. The rig's hoisting capability was to. The rig was connected to the well. Employee #1 grasped a chain to restrain the unit's well-connecting hardware to keep it from interfering with the test. He was standing on the unit base almost directly under the unit's horsehead. As the rig operator started the first upstroke, a connector on the hoisting line caught the horsehead, causing it to dislodge and fall. A bolt to restrain the horsehead to the unit had not been installed. Employee #1 was struck in the head by the horsehead as he tried to evade it. He died shortly thereafter from a crushed head and massive bleeding.