Legendary comic book artist and the co-creator of Spider-Man, Steve Ditko, has died at the age of 90. The New York Police Department told Variety magazine that Ditko was found dead in his apartment on June 29. The cause of death is not clear.

“Steve Ditko was one of the most amazing creators in the history of comics, and showed us there is a hero in all of us. Our hearts go out to his loved ones, and everyone who knew him,” DC Comics tweeted on Friday.

Marvel Comics Editor-in-Chief Stan Lee approached Ditko with the idea of the Spider-Man character while Ditko was working there in 1962. Ditko gave the character its iconic suit, red-and-blue colours and web shooters, Rolling Stone reported.

Lee and Ditko also created Doctor Strange in 1963. However, the artist left Marvel in 1966 due to differences with Lee. Ditko then began a stint at DC Comics, which resulted in the creation of Creeper, a superhero who would later join the Batman universe. He returned to Marvel in the 1990s to co-create the Squirrel Girl comic.

“Without Steve Ditko, there would have been no Spider-Man, no Doctor Strange, no Creeper, no Hawk and Dove, none of the black and white reprint comics I read in seaside resorts as a boy,” British novelist Neil Gaiman tweeted. “No The Question (which means no Rorschach). No Mister A. No mystery.”

“Steve Ditko was true to his own ideals. He saw things his own way, and he gave us ways of seeing that were unique,” Gaiman added. “Often copied. Never equaled. I know I’m a different person because he was in the world.”