EE was using a 16 pound sledge hammer to straighten a metal guard. As he swung the hammer, he felt a pop and pain in his left shoulder. EE continued to work his scheduled shifts but due to continued discomfort he saw a physician on 01/09/15 and received an MRI. Diagnosed with 2 tendon tears. EE returned to work until 02/04/15, which was his first day away from work.