Reese Witherspoon is mourning the sudden death of her "Big Little Lies" director Jean-Marc Vallée, who died on Sunday at age 58.

"My heart is broken. My friend. I love you," Witherspoon wrote via her Instagram Stories on Monday while including a photo of herself with the filmmaker.

Vallée died "suddenly" at a cabin on the outskirts of Quebec City over the Christmas holiday, sources relayed to Deadline. A cause of death has not been shared. 

Those close to Vallée further pressed to the outlet that the "Dallas Buyers Club" director was planning to host guests over the weekend when he was found the morning after Dec. 25.

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Other Hollywood mainstays also poured in tributes to Vallée, including fellow "Big Little Lies" star, Shailene Woodley, who described the news as "complete and utter shock."

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"My f–king god death is the worst," the 30-year-old actress wrote on her Instagram Stories. "But I guess somehow I know you will turn it into a grand adventure … one for the books. One I can’t wait to read & to watch when my time comes." 

Reese Witherspoon is mourning the sudden death of her ‘Big Little Lies’ director Jean-Marc Vallée, who died on Sunday at age 58. The two are pictured here in 2017. (Photo by Jeff Kravitz/FilmMagic)

She added, "It doesn’t make sense though dude. It doesn’t make sense. Maybe when we wake up tomorrow you’ll be there laughing saying it was just a satirical short film you made. That it’s not real."

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In a statement shared with The Hollywood Reporter, Nicole Kidman – another "Big Little Lies" star – said: "It’s hard to imagine someone as vital, energetic and present as Jean-Marc being gone. I’m shattered."

"He was at the center of my creative universe and I can’t overstate his significance to me," Kidman continued. "Jean-Marc was not only responsible for some of the most rewarding professional experiences of my career, but his friendship, kindness and love were an inspiring force I will carry with me. I will always cherish those nights filming above the crashing waves of Big Sur…it doesn’t get better than that. I am forever grateful for my time shared with this extraordinary human. Forever Jean Marc."

Laura Dern, who starred in the series as well, remembered the late director as one of the "great and purest artists and dreamers." "Our hearts are broken," she said.  

"Dallas Buyers Club" star Matthew McConaughey also took to social media to remember Vallée.

"With a gentle hand and heart Jean-Marc was a true receiver — he didn’t romanticize life so much as he saw life romantic — from the struggle to the pain to the wink and the whisper, love stories were everywhere in his eye," McConaughey wrote.

McConaughey's co-star Jared Leto said: "A filmmaking force and a true artist who changed my life with a beautiful movie called Dallas Buyers Club. Much love to everyone who knew him. Life is precious."

"Spy" director Paul Feig also tweeted, "My god, this is so unbelievably sad. What a huge loss. He was an incredibly talented filmmaker. Sending much love and condolences to his family. #RIPJeanMarc."

Director Jean-Marc Vallee, actress Reese Witherspoon, Author Cheryl Strayed and actress Laura Dern attend the premiere of Fox Searchlight's ‘Wild’ at AMPAS Samuel Goldwyn Theater on November 19, 2014 in Beverly Hills, Calif. (Photo by Frazer Harrison)

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Canadian Prime Minister Justin Trudeau, also wrote, "Jean-Marc Vallée’s passion for filmmaking and storytelling was unmatched – so too was his talent. Through his work and with his art, he left a mark in Quebec, across Canada, and around the world. My thoughts are with his family, friends, and fans as they mourn his sudden passing."