EE was installing a machine guard approx. 75 lbs. on a piece of Eq. on 4/12/11. EE's feet slipped on a hill of dust and he overextended his shoulder.Due to continued pain on 4/25/11 company made a Dr. appt. for him the EE RTW the next day. EE also received 2 Rx's and was waiting on X-rays when we met with him on 4/27/11 for the incident investigation. (See attachment)