In the episode titled 'Flight', Lexie Grey (Chyler Leigh) was dramatically killed off and Teddy Altman (Kim Raver) left to take up a chief position elsewhere.
Show creator Rhimes tweeted: "This finale was incredibly hard to write. I did not enjoy it. It made me sick and it made me sad.
"We end the season not knowing ANYTHING about the future. Except for two things. We know we are definitely saying goodbye to two of my favourite people: Chyler Leigh and Kim Raver."
On Lexie's death, Rhimes explained: "I love Chyler and I love the character of Lexie Grey. She was an important member of my Grey's family. This was not an easy decision.
"But it was a decision that Chyler and I came to together. We had a lot of thoughtful discussion about it and ultimately we both decided this was the right time for her character's journey to end."
Teddy, on the other hand, exited the show after Owen Hunt (Kevin McKidd) fired her to force her to take up the Metcom offer.
Rhimes stated: "Kim's series option was up and she was ready to give Teddy Altman a much-needed vacation. It's been a pleasure working with someone as talented and funny and kind as Kim.
"Everyone is going to miss her terribly. I like to imagine that Teddy is still out there in the Grey's Anatomy universe, running Army Medical Command and building a new life."
It was recently revealed that Ellen Pompeo, Patrick Dempsey, Sandra Oh and several others have signed new deals to return for season nine.
> Read Digital Spy's recap of the Grey's Anatomy season finale 'Flight'