EE WAS GRINDING WITH A 4 1/2"" GRINDER. THE EE STATES THAT HE IS UNSURE WHAT HAPPEN. ON FURTHER INVESTIGATION THE GRINDER WAS FOUND TO HAVE A WIRE WHEEL BEING USED TO CLEAN BOLTS. IT APPEARS AS THOUGH THE GRINDER KICKED-BACK. EITHER THE EE ATTEMPTED TO CATCH THE GRINDER WITH HIS FREE HAND OR THE GRINDER KICKED BACKINTO HIS HAND. HE ALSO STATED THAT IT HAPPENED SO FAST HE WAS UNSURE.