Grey's Anatomy season finale 2010 spoiler: Who died on Grey's Anatomy?

Thursday night's season finale of "Grey's Anatomy" featured a gunman on the loose at Seattle Grace. It was Mr. Clark, a guy from earlier this season who was convinced Derek Shepherd prematurely pulled the plug on his wife.

Watch the full episode online by clicking on the link that accompanies this page.

The biggest casualties in the bloodbath? Reed Adamson and Charles Percy, members of the Mercy West crew. They both died.

Meredith also learned she was pregnant, but had a miscarriage by the end of the episode. Here's a full recap:

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The show's first 10 minutes confirm everything we saw in the extended sneak peek: Meredith's pregnant and there's a gunman on the loose in Seattle Grace. The first victim? Resident Reed Adamson, the short-haired girl from Mercy West. Karev also gets shot, but appears to have survived. For now.

The shooter is Mr. Clark, the guy from earlier this season who blames Derek Shepherd for his wife's death. The whole hospital is on lockdown.

Meredith has not told Derek about her pregnancy yet. She asks Cristina to be the godmother and Cristina says yes.

In some accompanying story lines, Cristina and Owen are broken up and Mark Sloan still misses Lexie Gray. So much, in fact, that he basically saves her when the gunman goes on a brief rampage then disappears.

Karev's situation is looking less promising, meanwhile. He's still on the floor, possibly unconscious. Can Lexie and Mark save him? We'll see.

The shooter walks into a hospital room occupied by Dr. Bailey, a patient played by guest star Mandy Moore and Charles Percy from Mercy West. Mandy Moore pretends to be dead. Dr. Bailey hides under the bed.

The shooter has a conversation with Dr. Percy. He asks Percy if he's a surgeon. Percy says yes and gets shot. Then, the shooter finds Dr. Bailey and pulls her out from under the bed.

"Are you a surgeon? Answer me!" the shooter says. Bailey says no, she's a nurse. The shooter apologizes, loads his gun, then leaves.

Lexie and Mark are still taking care of wounded Alex. The Callie/Arizona story line? They're stuck in the pediatrics are together during lockdown. Cue the heart-to-hearts.

Percy isn't dead yet. Dr. Bailey and Mandy Moore must attempt to save him. Famous last words: "We're all going to be fine."

Oh yeah, the Owen/Teddy story line: They're operating on a patient, but can't leave the operating room. Teddy says she knows Owen is in love with her and Cristina. He has to decide.

Meredith and Cristina are stuck in a small room together. Cristina looks out the window and realizes the shooter is the same guy she met earlier in an elevator. He asked her where Derek's office was. Cristina tells Meredith the shooter is looking for Derek.

Mr. Clark finds Derek and says, "You hurt me when you decided to kill my wife."

Meanwhile, in the Sloan-Lexie-Alex situation, Alex needs a blood transfusion. Lexie leaves the room to go get it, even though the shooter is still on the loose.

Uh-oh. Mr. Clark is now pointing gun at Derek...while Cristina and Meredith watch from a distance. Pause.

Time for an update on the Mandy Moore-Bailey-Percy room. Percy is convinced he's going to die. Bailey says they can save him. Mandy Moore must hold his hand.

Back to Mr. Clark pointing a gun at Derek. Derek tries to reason with him by telling him he lost his father when he was little. "I'm a human being. I make mistakes. I'm flawed," Derek says. "You're a good man. I can see that in your eyes. Can you see it in mine?"

Mr. Clark lowers his gun...until resident April Kepner runs in and interrupts the scene. With that, Mr. Clark shoots Derek. The shooter tells April to run away.

Meredith has come to Derek's side and she's panicking. She and Cristina are bringing Derek to the OR with frazzled April's help.

How did Lexie fare on her trip to the blood bank? Well, she runs into Mr. Clark along the way. He says he wants to shoot her. He points the gun...and gets shot by one of the special agents in the hospital. Phew. I'm glad Lexie didn't die.

Now, it's time for Mr. Clark to interact with Callie and Arizona in pediatrics. Callie gives Mr. Clark some bandages for his wound. "Take them and go," she says. He thanks her and leaves. Then, Callie consoles a scared little girl patient by telling her about Arizona's super-magic smile.

The Bailey-Mandy Moore-Percy situation is not looking good. Lots of blood.

Then, we're back to Derek. He needs immediate assistance. Cristina's going to be his surgeon! "For a resident, I'm very good," she says. Cristina doesn't want Meredith in the operating room. April has to make sure she doesn't come in.

Back at the Alex-Lexie-Sloan room, Lexie has returned unharmed from the blood bank and Alex has had a change of heart. He never wants Lexie to leave. Morning after note: One very attentive reader reminded me Alex called Lexie "Iz," as in his ex-wife Izzie, during this scene. Lexie is still smitten, however. "We're always going to be together, OK? Always," Lexie says. Meanwhile, Sloan looks on with some sad puppy dog eyes.

Outside, Dr. Webber has avoided the security barricades and entered the hospital. Teddy and Owen evacuate the hospital, but then Owen realizes Cristina is still inside. Teddy tells him to go in and get her. "It's OK to choose," she says. So Owen goes back inside.

Lexie, Mark and Alex have evacuated. Cristina is operating on Derek. There's bullet lodged right next to his aorta.

Mandy Moore, Bailey and Percy are almost out. Believe it or not, Percy is still alive. But wait: The elevators are off. They're trapped. Bailey freaks out. Percy is dying. "Mary and I are going to be with you the whole time. You are not alone. You hear me?" Bailey says.

Owen comes back into the hospital. He's all set to help Cristina with Derek's surgery. Everything will be great. Oh wait, the shooter's in the operating room.

"Stop fixing him. Let him die," Mr. Clark tells Cristina. She can't stop, and Mr. Clark threatens her again. Owen steps in. "That is the woman that I love, you shoot her, you touch her and I will kill you," Owen says. Then, the shooter alternates between pointing the gun at Cristina and Owen.

"I came here for justice, an eye for an eye," Mr. Clark says. Meredith steps into the room and says he should shoot her instead. "I'm your eye for an eye."

"Tell Derek that I love him and I'm sorry," Meredith says. Then, Cristina says he shouldn't shoot a pregnant woman. It's chaos, so Mr. Clark just shoots Owen.

Then, in Mr. Clark's presence, all the residents hold up their hands and let Derek's heart slow down. It's Dr. Jackson Avery's idea. They convince Mr. Clark that Derek has died. He believes it and walks away. When he's gone, Cristina and company quickly begin trying to save Derek again.

As if that wasn't a big enough bloodbath for you, Percy is now dying. For real. He begs Bailey and Mandy Moore to tell Reed he loves her. Clearly, he doesn't know she died. As Percy dies, he tells Bailey, "You were always my favorite doctor. I thought you should know."

With that, we see Meredith and April saving Owen. Suddenly, Meredith is in pain. Blood is falling down her legs. She's having a miscarriage, but she keeps operating.

With 10 minutes left, we find confrontation between Webber and Mr. Clark in a poorly lit room. Mr. Clark asks Webber to open his flask so he can have a drink. "The funny part is, I didn't need a drink until now," Mr. Clark says. He only has one bullet left. "See, I was going to kill you...and then I was going to shoot myself. But I only have one bullet left," Mr. Clark tells Webber.

Webber pours out Mr. Clark's flask of vodka. "You have a choice to make. Me or you?" Webber says. "I'm not afraid to die. The question is: Are you?"

Then, the screen goes black and we hear a gunshot.

Four minutes left. Time for a final heart-to-heart between Callie and Arizona. The tragedy brought them together. "I don't want to have kids if it means I can't be with you," Callie says.

Arizona responds, "No, we'll have kids."

Alex is alive, Derek is stable, and I think Owen is, too. Oh yeah, Chief Webber is alive, too. So the gunman shot himself.

The show ends with Meredith throwing away her positive pregnancy test.

Wow, so much drama. Weigh in, viewers: What did you think?

This story was originally published May 20, 2010 at 3:45 PM with the headline "Grey's Anatomy season finale 2010 spoiler: Who died on Grey's Anatomy?."