Len Wein, comics writer, editor, and co-creator of your favorite characters like Wolverine and Swamp Thing, has died at the age of 69.

Though the cause of death is still unknown, there have been an outpour of tributes from the comic book community online.

Marvel and DC Comics also confirmed the news and issued statements paying homage to Wein.

Wein, who was born in New York City, started his career freelancing with DC Comics around the age of 20. His career brought him to Marvel Comics, before returning to DC again. He’s credited for launching a new version of X-Men in the ‘70s, which included new characters Wolverine, Storm, Nightcrawler, and Colossus drawn by artist Dave Cockrum.

Huge Jackson, the actor best known for his role as Wolverine in the X-Men film series, shared a heartfelt tribute on Wein.