EE WAS CLEANING UP AND WENT TO DUMP TRASH CONTAINER. HE STOPPED FORK LIFT SHORT OF A DROP IN PAVEMENT AND EMPTIED CONTAINER. WHEN HE RETURNED TO THE FORK LIFT AND STARTED TO BACK UP, THE FORK LIFT ROLLED FORWARD INTO THE DROP OFF. HE HIT THE ACCELERATOR AND THE LIFT SWUNG SHARPLY TO THE RIGHT AND PINNED HIS ARM BETWEEN A SUPPORT BEAM AND THE LIFT ROLL CAGE.