THE EE INITIALLY INJURED HIS LEFT SHOULDER ON 2-5-01. THE EE WORKED AT FULL CAPACITY UNTIL 2-13-01. HIS LOST TIME BEGAN 2-13-01. THE OPERATOR BECAME AWARE OF HIS INJURY ON 2-21-01 WHEN THE INI TAL REPORT WAS COMPLETED FOR THE CO. THE EE WAS HELPING HIS PARTNER ON A ROOF BOLTER. THE INJURED EE WAS HOLDING A BOLTING MACHINE WRENCH AND THE WRENCH SLIPPED & STRAINED HIS LEFT SHOULDER.