EE HAD JUST GOTTEN OUT OF THE CAB OF THE ROOF BOLTER AND WAS GETTING READY TO HAND HIS CABLE AT THE TIME OF THIS INCIDENT. HE STATED THAT THE TOP WAS AROUND 8' HIGH OR HIGHER AND THAT HE WAS G OING TO DRIVE SPADS IN THE RIB TO HANG THE CABLE FROM. HE STATED AS HE WALKED BY THE BOLTER A ROCK WEIGHING APPROX 100# FELL FROM THE ROOF FROM BETWEEN TWO ROOF STRAPS AND STRUCK HIM ON THE T