This is very sad, I met him once. He came to my animation school and gave a lecture about the business. Talked about how Hanna Barbera wanted to do a mystery show and he had to design the characters. They asked can you do it, and he said "you always say yes if they ask you to do something, storyboards/character designs/ animation/ back grounds/ anything, say yes." So he did, but he knew it was missing something, so it was his idea to do Scooby Doo.
He mentioned that many of the animators and such from that time period at Hanna Barbera had died. He was one of the few left, to go and give lectures at schools.
Afterwards people asked for autographs, he drew so many Scooby Doos that day. I asked him about merchandise, I think, because he mentioned how that is where cartoon shows makes all their money, thats why Sponge Bob is everywhere. I also asked him about getting tired of drawing Scooby Doo all the time, I think he sort of agreed. He mostly talked and I listened.
I am not a big fan of Scooby Doo or many of the cartoons he worked on or created, but I really respected the man. I still have the Scooby Doo he drew me framed in my room.
He will be missed a great deal.