Abstract: Employee #1, a 16-year-old mechanic's assistant, and his boss were installing and tightening the plug for the brake canister on the driver's side of a tub grinder. The driver assigned to transport the grinder to an off-site location had used a Peterbilt tractor to bring it from the rear yard to the garage, where the plug could be tightened. Once the driver pulled up to the garage, he exited the cab and left the vehicle running. The mechanic crawled underneath the tub grinder between the second and third axle, but came out once he discovered he had the wrong size wrench. According to the mechanic, he explained to Employee #1 that he was tightening the plug on the brake canister they had replaced one month earlier. The driver was walking around the tractor and tub grinder and he and the mechanic agreed that he would pull the tractor and tub grinder around to the other side of the building for refueling while the mechanic obtained another wrench. Apparently Employee #1 did not hear this conversation. While the mechanic and the driver went their own ways, he obtained a wrench from the garage and climbed underneath the tub grinder. Shortly thereafter, the driver put the vehicle in gear and pulled it forward, crushing and killing Employee #1. Causal factors in the accident include failure to chock the wheels, leaving the vehicle running while work was ongoing, and lack of training to look underneath a vehicle prior to moving it.