There's a man with a gun on 'Grey's Anatomy' (Thu., 9PM ET on ABC). Could this be the end for some of the characters on the show?

[Spoiler alert.]

An angry, grief-deranged widower stalks the halls of Seattle Grace Hospital. He blames Dr. Derek Shepherd (Patrick Dempsey) for he death of his wife. And now, he's out for revenge. The widower shoots at doctors, commits murder, and then finally confronts Derek.

Meanwhile, Derek's own wife Meredith (Ellen Pompeo) discovers that she's pregnant. Derek is shot by the intruder, and the villain is still on the loose. Suddenly, everything is a matter of life and death. Will Derek survive? Will Meredith survive? Will their baby survive?