“Simpsons” co-creator Sam Simon died in his Los Angeles home after a long battle with colon cancer, Variety reported Monday. He was 59.

Simon was an animal rights activist who was surrounded by his family and his dog when he died Sunday. "For those of us who knew him, his voice will forever echo in our minds, his sense of humor will continue to make us laugh, and his compassion and generosity will continue to impact our lives,” the Sam Simon Foundation said in a statement to TMZ.

“Sam, you will be missed by many, but there is a particular sadness among our clinic staff. We have been together for so long, and your absence will forever leave a void in our lives,” the foundation added.

Simon was diagnosed with colon cancer in 2012 and was not silent about his disease being terminal. Still, fans on Twitter were shocked and upset to hear of his death. His name quickly became a top-trending topic on the social media site minutes after news of his death went viral.

Simon continued to tweet until the week before he died. He described himself as “just a kid from Beverly Hills that got lucky.”

He shared a photo of pop star Britney Spears swimming with dolphins, and said he found it hard to believe there wouldn't be a backlash for swimming with the mammal.

One of the last photos the “Simpsons” co-creator posted of himself was one of him getting his lungs drained. “Draning [sic] lungs!” he wrote March 1. He can be seen with one hand on his head as a doctor cleared his lungs.

For his final tweet to his 50,000 followers, he wrote: “Apple pan deliverr [sic].”

Fans quickly took to Twitter to mourn his death. Celebrities like Hank Azaria, who voices several characters on “The Simpsons” tweeted: "Rest in peace and thank you for 'The Simpsons,' Sam Simon." Other tweets and messages have been shared below: 

Follow me on Twitter @mariamzzarella