A 41-year-old male plant production supervisor (the victim) died after being crushed between the left boom lift arm and the front chassis of a skid-steer loader (Photo 1). The skid-steer loader had been dropped off that morning by a rental agency representative who gave basic operating instructions to the victim and the plant maintenance supervisor. Later in the day the victim, who had been in the plant, was exiting the rear of the plant when he observed the maintenance supervisor having some difficulty operating the loader. The victim approached the loader to assist. The maintenance supervisor had no prior skid-steer loader experience and had been running the loader for approximately 10 to 15 minutes. He told the victim that he thought there was something wrong with the hydraulic system. Both men attempted to troubleshoot or identify the problem. The victim, who had some skid-steer loader experience and had been operating the loader earlier that morning, told the maintenance supervisor to raise the boom. While talking to the maintenance supervisor about a control handle on the right side of the operatorís seat, the victim moved under the boomís lift arm to show him the control. Reaching across the front of the loader cab from left to right, the victim moved his arm to the right side of the maintenance supervisor, reaching for the auxiliary boom-control lever. From this point the exact sequence of events is not clear, however, for some reason the boom and bucket assembly came down rapidly on top of the victim, who was between the left boom lift arm and the front chassis of the loader. During the incident a hydraulic line ruptured at the elbow fitting on the left boom lift arm, spraying the maintenance supervisor and cab with hydraulic fluid. Two witnesses rushed to the scene. The maintenance supervisor raised the boom and bucket assembly and the victim fell to the ground. He then moved the loader away from the victim and shut it down. Plant personnel arrived and began cardiopulmonary resuscitation (CPR) and called 911 for emergency assistance. Emergency response personnel arrived within minutes and continued CPR. The victim had sustained serious trauma to the head and chest and was pronounced dead at the scene. NIOSH investigators concluded that, to prevent similar occurrences, employers should: 1) ensure that employees recognize the hazard of working under raised, unblocked machine components by providing appropriate training in the safe operation of all machinery and equipment; 2) carefully evaluate the knowledge and experience of their employees when choosing whether to rent equipment for them to use or to obtain the services of specialist contractors. Additionally, rental agencies should; 3) ensure that customers are informed of safe operating procedures and proper use of equipment safety devices when machines are delivered.