Considering we've got two episodes of Grey's back-to-back to create this two-hour season finale, they don't waste any time getting down to business. And what would that business be, exactly? Well, that would be thinning down this overlarge cast. And how would they do that? With a shooter in the hospital.

Of course this means that we start out with a bunch of extra happy people -- Meredith finds out that she's pregnant, and though it's an accident she's happy about it, if a little freaked out, and Cristina is thrilled for her. She doesn't tell Derek yet though because he's in a bad paperwork mood when she gets to his office, so she makes plans to tell him that night. Unfortunately, she has no idea that Gary Clark -- the one whose wife was unplugged and who filed the wrongful death suit against the hospital -- has arrived at the hospital armed and is looking for her husband. He tries to ask a few different people where Derek is but everyone is busy with a bunch of crazy emergencies all at once and everyone he asks brushes him off. When he finds Reed getting supplies and she's a snot to him, he announces his intentions for the day by shooting her basically point-blank in the head. Alex hears the commotion and comes around the corner and gets shot in the chest for his trouble. He manages to pull himself to the elevator and climb in, probably figuring someone will find him there sooner than in a darkened corridor. As April is going about her business she trips over something and when she realizes it's Reed's body, she runs to Derek's office in shock and finally manages to tell him what's going on. The protocol is to put the hospital on lockdown, so that's what happens, trapping everyone inside on their floors (and trapping a very helpless feeling Richard outside, as he was having breakfast and not at work yet when it all went down). Before everyone realizes what is happening and the lockdown is issued, Gary and Cristina wind up in an elevator together and he asks her how to find Derek; she's feeling pensive about her breakup with Owen and Mere's pregnancy and so is surprisingly calm and nice to him, giving him directions. In thanks for that he keeps his gun hidden and they wish each other good day before he goes off to continue his murderous rampage.

Gary starts wandering about looking for Derek and starts shooting people in his path, but he seems to be making a special effort to get surgeons. Mark and Lexie are together when he starts firing into a crowd and after he leaves escape to an elevator, where they find Alex, who looked very horrifyingly dead for a moment. He's alive, but not doing well, and they take him to a conference room to work on him; after realizing the bullet is still in his chest and giving him a chest tube Mark realizes he needs blood, and Lexie decides to go get it since Mark is the one who knows how to treat Alex and therefore needs to stay with him.

Bailey and Percy are caring for Mandy Moore, who is in the hospital awaiting surgery and who has her cute husband Pete in tow. When she finds out she can't have surgery that day she sends him off to get her some pizza, and so he winds up trapped outside with Richard. Meanwhile, Percy leaves the room and finds out what's going on, so he runs in to warn Mandy and Bailey. In some quick thinking Bailey has him hide and Mandy play dead while she hides under the bed, and it works for a bit until Percy makes a noise in the bathroom. Gary goes in there and shoots him when he finds out Percy is a surgeon, and then when he comes back out he realizes Bailey is hiding and pulls her out from under the bed (the shot ABC has been milking for a week now). He demands to know if she's a surgeon but she manages to squeak that she's a nurse, and so he leaves her unharmed and leaves. She then has to try and care for Percy who has a gunshot wound to the abdomen, but she's understandably a bit of a mess and it's a fight to hold herself together, especially as her assistant is Mandy, who can only barely help because she is so panicked. They both do the best they can, though, and Bailey tells Percy sternly that he's not dying though obviously he (and probably she) think differently.

Teddy and Hunt have a patient who was shot after a fender bender -- my guess is that he ran into Gary on his way in to the hospital -- and the lockdown comes while they are in surgery so no one checks their pagers and knows what's up. Derek comes and tells only Avery, with instructions for Avery to tell them only after surgery is over. Hunt doesn't take being kept in the dark very well and eventually decides to take his patient to ICU anyway because [some medical situation that I will understand better when I watch this again for the full recap] and Teddy goes with him, ignoring his trying to order her to stay. In another tense wing of the hospital, Callie and Arizona are locked down with Graciella (who we haven't seen in months and I kind of fear for her now) in pediatrics with only a few nurses and a ton of kids. They decide to keep the kids all together in the playroom but fight with each other the whole time, because Callie has decided this is a good time to talk about their relationship woes. They're brought back to the present by one patient whose appendix explodes, so my guess is we're seeing more hallway surgery in the next hour.

Finally, Cristina and Meredith ignore the lockdown order as they figure it's a drill, and Derek finds them wandering about and chatting. He tells them about the shooter and has them hide in a supply closet, where they are almost caught by Gary, who Cristina recognizes as the man in the elevator. But he doesn't come in and instead finds his way to Derek, and they have an artsy standoff on the walkway to his office, where Derek tries to talk him out of shooting him. Cristina and Mere have made their way out of the closet and can see but not hear what's happening, which is that Derek almost manages to talk Gary out of shooting him. Unfortunately April, who Derek has ordered to stay in his office, runs out, relieved that he's back and not seeing Gary there. That movement breaks the spell, and Gary shoots Derek directly in the chest, while Cristina holds a screaming Mere back on the other side of the floor. And with that, we head to the second episode. --Lauren S