Abstract: Employee #1 had just finished making a welding pass on the back side of the blade on a John Deere 750 bulldozer. He removed his welding helmet and laid it on the pavement of the driveway in which he was working. Employee #1 heard a noise from the fast-moving vehicle traffic behind him on the street. He then heard a loud noise like a vehicle firing from behind him. At about the same time, something struck him on the side of his head. Employee #1 tried to find his glasses, which had been knocked off, but was unable to locate them. He went to the machine shop for his other set of glasses and then walked to the main office, where he met a coworker who rushed him to the hospital. Employee #1 sustained a concussion and various cuts and lacerations. No object was found that might have struck Employee #1 on the head. The local police also investigated the event. It is not believed that the accident was a result of the work environment.