Please answer the following question: Extract the answer to the following question from the movie plot. If the question isn't answerable, please output "Can't answer". Question: WHO GETS KILLED BY FROST? Title: Source Code Movie plot: U.S. Army pilot Captain Colter Stevens (Jake Gyllenhaal), last aware of being on a mission in Afghanistan, wakes up on a commuter train[6] to Chicago, at 7:40 am. To the world around him including his traveling partner Christina Warren (Michelle Monaghan) and the bathroom mirror he appears to be Sean Fentress, a school teacher. As he comes to grips with this revelation, the train explodes, killing everyone aboard. Stevens regains consciousness inside a dingy dim cockpit, leaking oil. Communicating through a video screen, Air Force Captain Colleen Goodwin (Vera Farmiga) verifies Stevens' identity, and insists he stay "on mission" to find the bomber before a large "dirty bomb" hits downtown Chicago in six hours. Inside the "Source Code" experimental device designed by scientist Dr. Rutledge (Jeffrey Wright), he experiences the last eight minutes of another compatible person's life within an alternative timeline.[a] Stevens is unwillingly sent back into the Source Code repeatedly in frustrating, exhausting attempts to learn the bomber's identity. He tries to warn authorities on the train and flee with Christina, escaping the explosion. Other times he cannot locate or disarm the bomb and dies on the train. But Rutledge insists the alternate timeline is not real. It is revealed that he has been "with them" for two months since being reported killed in action in Afghanistan. He is comatose and missing most of his body, hooked up to neural sensors. The cockpit capsule is in his imagination, his brain's way of making sense of a missing environment. A confused and frustrated Stevens asks, "As one soldier to another, am I dead?" Angry to learn that he is on life support, he asks to be disconnected after the mission. Rutledge agrees. Stevens catches the bomber Derek Frost (Michael Arden), who leaves his wallet behind to fake his own death, and gets off at the last stop before Chicago. In one run-through, Frost kills both Fentress and Christina, and flees in a rented white van. Stevens remembers the license...
Answer:
FENTRESS AND CHRISTINA.