Peyton List, Yara Shahidi mourn late actor Cameron Boyce

July 7 (UPI) -- Hollywood is mourning the death of 20-year-old Disney Channel actor Cameron Boyce this weekend.

His family confirmed Saturday night that the Jessie and Descendants star suffered a fatal seizure in his sleep.

He had been undergoing treatment for a medical condition at the time of his death.

Adam Sandler, who played Boyce's father in two Grown Ups movies, was one of the first celebrities to take to social media to express their heartbreak.

"Too young. Too sweet. Too funny. Just the nicest, most talented, and most decent kid around," Sandler tweeted Sunday.

"Devastated by this news. Cameron was brilliant, sensitive and a blazing talent. I'm lucky to have spent time with him this year, filming him for a documentary. My heart goes out to his lovely family. What a tremendous loss," actor and filmmaker Alex Winter said.

"I did not know Cameron Boyce personally, but it looks like he was someone who exuded wonderful, positive feelings and was a role model to many. Let his legacy live on and inspire millions more to carry themselves in the same way. He will be missed, but will still always be here," wrote singer Charlie Puth.

Peyton List, who played Boyce's sister on Jessie, remembered the actor on Instagram as "the boy who left everyone feeling hopeful and full of love."

"He lifted everyone around him, and inspired/pushed me to be a better person," her message said.

"Still in shock that we've lost this light I've known you since we were four and since that moment it has been clear how talented/ how kind/ how full of energy and love you are. One of our first jobs together I was princess jasmine and you were buzz lightyear which is apropos because throughout the years your brilliance has only grown stronger and more unstoppable. Your spirit has left an indelible impression on everyone lucky enough to know you and I'm grateful to be one of them," said black-ish star Yara Shahidi in her own Instagram post.