Lexie takes part in a surgery on Alison Clark (Caroline Williams) and informs her husband Gary (Michael O'Neill) that it was a success, only for Alison to suffer a stroke and fall into a coma that Derek and Webber state she is unlikely to wake from. As Alison had signed a DNR form, Lexie is forced to turn off the machines keeping her alive despite Gary's pleas for her to stop. After failing in an attempt to sue Seattle Grace Mercy West, a grief-stricken Gary Clark later returns to the hospital with a gun, seeking revenge on Derek, Webber, and Lexie. Mark shields Lexie during the shooting and the pair attempt to save a critically wounded Alex. Lexie heads out into the evacuated hospital to search for supplies and comes face-to-face with Clark. Before Clark can shoot her, however, a SWAT team member wounds him and Lexie manages to escape. Lexie and Mark proceed to save Alex's life, during which Lexie realizes that Alex is still in love with his ex-wife Izzie, as he calls for her while delirious and on the verge of death. After having a conversation with Webber, Gary Clark eventually commits suicide, having killed 11 people and wounded another 7 as well as causing Meredith to suffer a miscarriage.