'Yellowstone' spinoff 'Marshals' shocks fans by killing off major Dutton family member in premiere

The "Yellowstone" spinoff "Marshals" killed off a key member of the Dutton family during its premiere episode March 1.

During the premiere episode, "Piya Wiconi," Luke Grimes' Kayce Dutton visited a grave belonging to his wife, Monica Dutton.

"I miss you, baby. I miss my wife - my best friend. My only friend," Kayce said of Monica, who was played by Kelsey Asbille in "Yellowstone."

Grimes told Parade that visiting Monica's grave was his favorite scene in the pilot.

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"The whole thing with Kayce and Monica, it's like Romeo and Juliet, star-crossed lovers sort of thing," Grimes said. "And even if she's not around physically, clearly she's still very much around. I mean, my favorite scene in the whole pilot is when he goes and visits her grave and sort of just speaks out into nothing to talk to her.

"So, she's very much a part of the show and very much honored, as people will see, throughout the first season. She gets revisited a lot."

In the episode, it was revealed that Monica died after a cancer battle, which may have been caused by toxic levels of pollution on the Indian reservation where Monica, Kayce and their son Tate lived.

Grimes revealed he was "heartbroken" to learn of Monica's fate in the spinoff. He had to work up the courage to call Asbille and inform her of the news.

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"It felt like, 'I don't even know what that would look like doing it without her, what that would feel like.' Kelsey's become one of my best friends. She's the coolest actor I've ever worked with. She's down to earth, sweet and kind to every other actor and the crew," Grimes told TV Insider.

"I worked up the courage to call. I didn't know how she was going to feel about it. I had to see how she was doing."

Grimes told the outlet the pair had a "great conversation" and "in true Kelsey fashion, she handled it like a pro and totally understood. She's going to do just fine."

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Fans were shocked to see Monica being killed off during the first episode.

"Crazy killing off Monica