Keith Giffen, the veteran comics author and artist who co-created characters such as DC’s Lobo and the Jamie Reyes version of the Blue Beetle as well as Marvel’s Rocket Raccoon, has died. He was 70.

Giffen’s family announced his death on Facebook Wednesday via a sardonic post pre-written by the comic book writer-artist: “I told them I was sick…Anything not to go to New York Comic Con, Thankx,’ adding “Bwah ha ha ha ha.”

His death was affirmed by longtime collaborator Paul Levitz. “The sad news is now official: Keith Giffen has gone off to create new worlds that are beyond our living reach,” Levitz wrote on Facebook. “Keith was probably the most fertile creative mind of our generation in comics. He had an infinite number of ideas, pouring constantly out.”

Levitz continued, “We did over 60 stories together. Many of them he made far better than they might have been with any other collaborator, because of his ideas and contributions to character moments and dramas. A few we had rough times on, but I think no more than could be expected in a long relationship.”

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Giffen is known for writing and drawing DC Comics‘ “Legion of Super-Heroes” in the 1980s and 1990s, along with co-creating alien mercenary Lobo with writer Roger Slifer for the early 1980s title “Omega Men.” In 1987, Giffen co-created the “Justice League International” series with J. M. DeMatteis and Kevin Maguire, and later created a spinoff in 1989 titled “Justice League Europe” with DeMatteis.

Prior to DC Comics, Giffen worked at Marvel in the 1970s, where he and writer Bill Mantlo introduced Rocket Raccoon in the pages of “Marvel Preview,” a black-and-white magazine. Rocket Raccoon would eventually become a part of the “Guardians of the Galaxy” and was voiced by Bradley Cooper in Marvel’s sci-fi film trilogy.

In 2006, DC reintroduced Blue Beetle as Jamie Reyes, a Latino high school student who gains superpowers when he bonds with an alien scarab. Giffen wrote Reyes’ early adventures with co-creators John Rogers and Cully Hamner. The character, played by Xolo Maridueña, headlined Warner Bros.’ “Blue Beetle” this past summer, becoming DC’s first Latino-led superhero movie.