'Descendants' Cast in 'Complete Shock' Over Cameron Boyce's Death Ahead of Third Movie Premiere

The 20-year-old actor, who was being treated for "an ongoing medical condition," died in his sleep due to a seizure

The cast of the Descendants franchise is reeling in the wake of their costar Cameron Boyce‘s sudden death.

A source tells PEOPLE the stars of the global smash franchise are grappling with the realization that Boyce died at the age of 20 over the weekend.

“Everyone is in a state of complete shock,” says the source. “The cast had a strong bond and this is unimaginable.”

Boyce, Dove Cameron, Sofia Carson and Booboo Stewart all reprised their roles for the upcoming third installment in the music-driven story about famous Disney villains’ children wrestling with whether or not they have inherited the evilness of their parents. Descendants 3 is set to premiere Aug. 2 on Disney Channel and DisneyNOW.

Boyce Cameron
Descendants 3. David Bukach via Getty Images

News of Boyce’s death, first reported by ABC News, was confirmed by the actor’s family on Saturday night.

“It is with a profoundly heavy heart that we report that this morning we lost Cameron,” a family spokesperson said in a statement to PEOPLE, revealing that his cause of death was related to “an ongoing medical condition.”

“He passed away in his sleep due to a seizure which was a result of an ongoing medical condition for which he was being treated. The world is now undoubtedly without one of its brightest lights, but his spirit will live on through the kindness and compassion of all who knew and loved him,” the family spokesperson said. “We are utterly heartbroken and ask for privacy during this immensely difficult time as we grieve the loss of our precious son and brother.”

Cameron Boyce
Paul Archuleta/FilmMagic

The tributes to Boyce, who also starred in the Disney Channel series Jessie, have been pouring in.

“My Love, Light and Prayers go out to Cameron and his Family. Cameron brought Love, Laughter and Compassion with him everyday I was in his presence. His talent, immeasurable. His kindness and generosity, overflowing,” wrote Descendants director Kenny Ortega.

Adam Sandler, who played Boyce’s father in the films Grown Ups and Grown Ups 2, also remembered the actor.

“Too young. Too sweet. Too funny,” he wrote on Instagram. “Just the nicest, most talented, and most decent kid around. Loved that kid. Cared so much about his family. Cared so much about the world. Thank you, Cameron, for all you gave to us. So much more was on the way. All our hearts are broken. Thinking of your amazing family and sending our deepest condolences.”