EE STATED THAT HE WAS INT HE PROCESS OF INSTALLING ROOF BOLTS IN THE FACE OF #7 ENTRY. HE STATED THAT HE HAD REACHED FOR A HALF-HEADER TO INSTALL ON THE CURTAIN SIDE WHEN A PIECE OF ROCK MEASU RING 3'X1 1/2'X1"" TO 4"" THICK FELL FROM BETWEEN THE ROOF BOLT PATTERN STRIKING HIS RIGHT HAND WHICH WAS RESTING ON THE ROOF BOLT STORAGE TRAY.