EE WAS GETTING ROOF BOLT SUPPLIES AT THE TIME OFTHIS INCIDENT. HE WAS LOOSENING A CHAIN BOOMER ON A LOAD OF PIN SUPPLIES AT THE TIME OF THE ACCIDENT. HE STATED THE TOP WAS VERY LOW ABOUT 8"" T O 10"" ABOVE THE LOAD OF BOLTS & PLATES. HE TWISTED THE CHAIN BOOMER TO THE SIDE & JERKED IT OPENWHEN IT POPPED OPEN IT TWISTED BACK UPRIGHT & SMASHED HIS HAND BETWEEN THE ROOF & BOOMER HANDLE