We've got confirmation from the family as well as his biographer, Sam Weller.
His grandson, Danny Karapetian, shared these words with io9 about his grandfather's passing: "If I had to make any statement, it would be how much I love and miss him, and I look forward to hearing everyone's memories about him. He influenced so many artists, writers, teachers, scientists, and it's always really touching and comforting to hear their stories. Your stories. His legacy lives on in his monumental body of books, film, television and theater, but more importantly, in the minds and hearts of anyone who read him, because to read him was to know him. He was the biggest kid I know."