Patrick Dempsey Patrick Dempsey

"Did that really just happen?"

That's what you may be yelling at your TV screen on Thursday, May 20 after watching the season finale of Grey's Anatomy.

Grey's Anatomy finale: Who is the shooter?

The two-hour finale finds a gunman terrorizing the hospital, claiming the lives of several beloved characters. For once, taking that old adage of "no one is safe" lightly is not an option.

Here are the five things you should know about the season finale. (Warning: Spoilers galore):

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1. A shooter rampages through the hospital, gunning for surgeons.
2. No, the promos are not misleading you: Meredith (Ellen Pompeo) is pregnant.
3. It's a huge episode for Cristina (Sandra Oh) and Meredith as they become more adult in their decisions and actions.
4. There will be many deaths, including those of people you know.
5. Amidst all the death, there will be a happy ending for a fan-favorite couple.

Which characters do you think we'll lose? And which couple do you want to have a happy ending? Discuss in the comments below.