PERSON WAS TRAMMING SHEAR BACK INTO THE SNAKE IN PANLINE FROM THE TAILGATE END OF THE FACE. THE SANDSTONE TOP BEHIND SUPPORTS BROKE AND FELL CAUSING A MASSIVE DISPLACEMENT OF AIR AND DEBRIS. THE BLAST OF AIR FORCED PERSON BACK AND HE FELL INTO SUPPORT STRIKING HIS RIB CAGE AND LOWER BACK AGAINST THE BASE LIFT JACK HOUSING ON BASE OF SUPPORT.