SpongeBob SquarePants creator Stephen Hillenburg died Monday, Nov. 26. He was 57.

The reported cause of death is ALS. Hillenburg revealed he had the neurodegenerative disease in March 2017 through a statement.

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“I wanted people to hear directly from me that I have been diagnosed with ALS. Anyone who knows me knows that I will continue to work on SpongeBob SquarePants, and my other passions for as long as I am able. My family and I are grateful for the outpouring of love and support. We ask that our sincere request for privacy be honored during this time.”

Today, Nickelodeon released a statement regarding Hillenburg’s passing:

“We are incredibly saddened by the news that Steve Hillenburg has passed away following a battle with ALS. He was a beloved friend and long-time creative partner to everyone at Nickelodeon, and our hearts go out to his entire family. Steve imbued SpongeBob SquarePants with a unique sense of humor and innocence that has brought joy to generations of kids and families everywhere. His utterly original characters and the world of Bikini Bottom will long stand as a reminder of the value of optimism, friendship and the limitless power of imagination.”

The network took to Twitter to state they will be holding a moment of silence.

“We are sad to share the news of the passing of Stephen Hillenburg, the creator of SpongeBob SquarePants. Today, we are observing a moment of silence to honor his life and work.”

Before launching Spongebob, he wrote and directed episodes of another Nickelodeon series Rocko’s Modern Life from 1993 to 1996.

From there, Hillenburg began working on Spongebob, and the first episode aired May 1, 1999. The series still produces new episodes and has released more than 250 to date.

Hillenburg also directed, wrote and produced 2004’s The SpongeBob SquarePants Movie. He later wrote and executive produced the 2015 sequel, The SpongeBob Movie: Sponge Out of Water.

A few years ago, Nickelodeon shared an interview with Hillenburg where he discussed how his interest in Marine Biology inspired the hit show. You can watch it in full below.

Our thoughts are with Hillenburg’s family and friends at this time.