joins his fellow physicians as a resident. 2 new characters are introduced, former United States Army trauma surgeon Dr. Owen Hunt, and pediatric surgeon Dr. Arizona Robbins. Hunt becomes a love-interest for Yang, while Robbins begins a relationship with Torres. When Stevens is diagnosed with stage IV metastatic melanoma, she and Karev get married at the conclusion of the fifth season. In addition, Meredith and Shepherd marry, with their vows written on a blue post-it note. O'Malley dies in the premiere of the sixth season, due to injuries sustained from saving a woman from being hit by a bus, and Stevens later departs Seattle following a communication breakdown with her then-husband Karev following the Seattle Grace merger with Mercy West Hospital. Several new characters are introduced as Seattle Grace Hospital merges with Mercy West Hospital. Residents April Kepner, Jackson Avery, Reed Adamson, and Charles Percy, all transfer to Seattle Grace Hospital from Mercy West Hospital, and Avery has a brief relationship with Lexie, until she reunites with Sloan. Subsequently, Teddy Altman is introduced as the new Chief of Cardiothoracic Surgery. In the season 6 finale, a deceased patient's grieving husband embarks on a shooting spree at the hospital, injuring Karev, Shepherd, and Hunt, and killing residents Adamson and Percy. In the shooting's emotional reverberations, Yang and Hunt abruptly marry, not wanting to risk separation. Torres and Robbins eventually wed, officiated by Bailey. In season eight, Webber steps down as Chief of Surgery and allocates his job to Hunt. As the final year of residency for Meredith, Yang, Karev, Kepner and Avery is coming to a close, the doctors are all planning to relocate to different hospitals to pursue their specialty careers. However, all plans are put on hold when several doctors from Seattle Grace Mercy West Hospital are engaged in a plane crash, which kills Lexie and endangers Meredith, Shepherd, Yang, Sloan and Robbins. At the conclusion of the eighth season, Altman is courteously fired by Hunt as she struggles to decide whether or not to take the job as Chief at the United States Army Medical Command (MEDCOM). In the season 9 premiere, Sloan dies due to sustained injuries from the plane crash following a brief relapse of temporary health ("the surge") and the remaining characters work through their post traumatic stress and Arizona Robbins's loss of limb by way of suing Seattle Grace Mercy West, as the hospital