Was pulling electric cords and hanging them in the rack on a bin. Thought that is was a pulled muscle. On 8/10 went to doctor and said do physical therapy. On 9/6 was placed on light duty because no progress. On 11/9 reached out of dump truck to shut lime bin off and got pain in shoulder. Had MRI same day and on 11/10 was diagnosed with left torn rotator cuff. Surgery 12/13.