Leo D. Sullivan, an Emmy-winning pioneer in animation who worked on scores of cartoons over the course of his 50-year career, has died at the age of 82.

Kindly continue reading to find out his cause of death.

Leo D. Sullivan’s cause of death: How did Leo D. Sullivan die?

Sullivan died of heart failure on March 25 at Kaiser Permanente West Los Angeles Medical Center.

Sullivan’s animation, storyboarding, directing, and producing skills have helped bring characters to life throughout his career. His credits include “Hey, Hey, Hey, It’s Fat Albert,” “The Incredible Hulk,” “My Little Pony,” and “Flash Gordon,” as well as firms such as Hanna-Barbera, Warner Brothers, and Spunbuggy Works. Sullivan worked on the opening animation for the 1971 film “Soul Train.”

In 1952, the Lockhart, Texas native relocated to Los Angeles and began his career running errands for “Looney Tunes” animator Bob Clampett. In the 1960s, Sullivan collaborated with veteran Disney animator Floyd Norman to co-found Vignette Films, a firm that produced educational videos about historical Black individuals for American School children.

The two would go on to start AfroKids, a website and streaming service dedicated to offering “a spectacular experience for the entire Black family.” Sullivan just established his own charity, Leo Sullivan Multimedia Corp.

Sullivan has been honored twice by the Black Filmmakers Hall of Fame in Oakland, California, and his artwork has been featured at the San Francisco Cartoon Museum and the Los Angeles African American Museum. For three years, he also taught digital animation and 2D animation at the Art Institute of California-Orange County.

His wife Ethelyn, daughter Tina Coleman, and son Leo D. Sullivan Jr. survive him.