GREY'S ANATOMY - "Disarm" - News of the incoming mass causalities after a gunman opens fire at a local college hits the staff hard when they must spring into action, even while their own wounds are still fresh; and Arizona does not receive a warm welcome home at the hospital, on "Grey's Anatomy," THURSDAY, JANUARY 6 (9:00-10:01 p.m., ET) on the ABC Television Network. (ABC/ADAM LARKEY) JUSTIN CHAMBERS, JAMES PICKENS JR., JESSICA CAPSHAW