INJ WORKER & HELPER WERE REMOVING SLING FROM IBEAM PLACED ON DUNNAGE. THE CRANE OPERATOR MISSED THE HAND SIGNAL & BOOMED UP INSTEAD OF CABLING UP-THE SHADDE WAS NOT REMOVED FROM THE SLING PRI OR TO USING THE CRANE TO PULL THRU THE SLING FROM UNDER THE LOAD. THE BEAM FELL OVER & STRUCK THE HELPER ON THE RT TIBIA.