Fans of the "Descendants" movie franchise have had today's date marked for some time, as "Descendants 3" premiered on Disney Channel -- but the occasion was bittersweet.

Cameron Boyce, one of the film's stars, died last month in what the Los Angeles County coroner determined was sudden unexpected death in epilepsy.

After the movie ended, Disney Channel aired a moving tribute to the 20-year-old actor, which include footage of him with his co-stars and even a moment from an early audition.

"You mean everything to us," read the final slide.

(MORE: How the 'Descendants 3' cast became an 'extended family')

Boyce, who played Carlos in all three "Descendants" films, left his mark on fans and those who loved him, including "Descendants 3" actresses Dove Cameron and Sofia Carson.

"[Boyce] is the hardest person to put into words," Cameron told "Good Morning America."

"He was pure happiness and pure joy," added Carson. "I feel like none of us will ever be able to express exactly the kind of heart that Cameron was."

To honor Boyce’s memory, his family launched The Cameron Boyce Foundation, which will provide “young people artistic and creative outlets as alternatives to violence and negativity and uses resources and philanthropy for positive change in the world,” according to their website.

"I think that as absolutely heartbreaking as this one is, it is a personal loss for so many young people who watch Disney," Cameron said. "I truly think the best thing we can do for them is to remember Cameron exactly as he was in -- in the most positive light -- but not to avoid it."