Cause of death: natural cause
Joseph Clemens Ruby (March 30, 1933 – August 26, 2020) was an American animator, writer, television producer, and music editor. He was best known as a co-creator of the animated Scooby-Doo franchise, together with Ken Spears. In 1977, they co-founded the television animation production company Ruby-Spears Productions. Ruby would work with Spears and would co-create several other shows including, Fangface, Dynomutt, Dog Wonder and Jabberjaw among others.
Ruby would meet Spears in 1959 at Hanna-Barbera, when the studio was being interviewed by Life Magazine and the two would start working together on animated shows. Before Ruby founded Ruby-Spears he would work with at several studios including Walt Disney Animation Studios, Hanna-Barbera, DePatie–Freleng Enterprises and with Sid and Marty Krofft.
In 1996, the Ruby-Spears studio closed, and Ruby would keep working with Spears up until his death on August 26, 2020. Spears would pass away three months later.
Source : Wikipedia