Shonda Rhimes explains why she killed McDreamy

California — Shonda Rhimes says it "wasn't easy or fun" to kill Patrick Dempsey's character off of ABC's Grey's Anatomy.

Dempsey played Dr. Derek Shepherd, a brain surgeon nicknamed McDreamy, who was Ellen Pompeo's love interest for 11 seasons on the long-running medical soap.

Speaking to TV critics Tuesday, the Grey's creator said she was faced with either having Shepherd leave Pompeo's Meredith Grey and taint their love story, or be killed off, keeping it intact.

"The only way to preserve what felt true to me was that Derek was gonna have to die," she said.

Pompeo said that the loss was an interesting challenge creatively because "those are the best scenes to play" as an actor.

She also pointed out the realism of the situation.

"So many people lose their spouses in a myriad of different ways and feel they can't get up again and to tell the story of how life goes on after... that's a story worth telling."

Earlier Tuesday, ABC President Paul Lee also addressed the polarizing choice to kill off Dempsey's character. "It was great to see Grey's Anatomy so relevant and taking the national conversation," he said.

Lee went on to say that "It was a difficult decision. Patrick obviously has lots of interests outside," referring to Dempsey's career as an amateur race car driver. "Shonda decided that was the way to go."

Rhimes teased that season 12 will be "lighter in tone" and shows Pompeo's Grey in a position she never thought she'd be in, as a widowed mother.

Grey's new season will premiere in the US in September. SA screening dates to be confirmed.