An employee transported glass to a jobsite. The installation crew unloaded the left side of the truck first. The last piece of glass weighed 300 pounds. Four employees picked up the glass from the truck. Once picked up, the injured employee started to untie the other side. This caused suspension to shift on the truck and glass panes estimated to weigh 750 lbs. fell off the truck onto the injured employee. The employee suffered a lower back fracture.