UPDATED with Dan Harmon tribute: J. Michael Mendel, an Emmy-winning animation producer best known for his work on The Simpsons and Rick and Morty has died. He was 54.

Mendel began working on popular Adult Swim series Rick and Morty when it launched in 2013. The cable network released a statement Monday calling him the “heart” of the show’s production team.

“All of us at Adult Swim are devastated by the untimely passing of Mike Mendel,” the statement began. “Mike was the heart of the Rick and Morty production family, his fantastic talent and wit will be sorely missed.”

“Mike was a universally respected Emmy-winning producer with over 25 years in the industry, who guided and supported a generation of artists, writers and creators and his absence will be felt by the entire community,” the statement continued. “Our deepest condolences go out to his family, friends and colleagues during this difficult time.”

Justin Roiland and Dan Harmon, Rick and Morty’s co-creators, shared emotional tributes on social media.

“My friend, partner, and line producer Mike Mendel passed away,” Roiland tweeted Monday. “I am devastated. My heart breaks for his family. I don’t know what I’m going to do without you by my side Mike. I’m destroyed.”

“I can’t handle seeing his cropped photo in headlines with the word dead in them, Harmon wrote on Instagram. “I hate the phrase RIP it makes me picture styrofoam tombstones at a Halloween party. Rick and Morty has lost Mike Mendel, a man that deserves a better obituary and in my angry opinion, a better god. That opinion is a projection of my shame. I took Mike for granted. He was always needed and he was always there. He’s going to be needed tomorrow and he won’t be there. The wound will scar but there will be a hole through everything we do from now on. I have only angry things to say for now, that’s how valuable mike was. I can’t keep editing these words so here’s a kitten and I’m gonna take a nap.”

Mendel won four Emmys for his work on The Simpsons and Rick and Morty.