The 20-year-old Disney Channel star died in his sleep following a seizure.
"To our angel, there are not enough words. There will never be enough words," Carson, 26, wrote alongside a black-and-white photo of Boyce. "I couldn’t bring myself to do this because doing this makes it real. Letting you go is not something I know how to do. And I just can’t fathom living in a world without you. I love you, Cam. And I will love you. Forever."
The actors' other Descendants co-star, Dove Cameron, also replied to Carson's post, writing, "I love you."
The 20-year-old actor's death came as a shock to many. His family revealed earlier this week that Boyce suffered from epilepsy.
On Thursday, Disney Channel announced that they would be canceling the Descendants 3 premiere planned for July 22 in wake of the star's death. Instead, The Walt Disney Company will make a donation to the Thirst Project, a philanthropic organization to which the actor was deeply committed. Disney Channel, with permission from the Boyce family, will also dedicate the telecast of Descendants 3 next month in his memory.
Since his death, a slew of Disney Channel friends and former co-stars have been honoring the actor. Cameron, on her end, posted a series of tearful videos remembering her longtime pal.
"Cameron was one of my favorite people alive in the world, though I know that's not unique to me. Cameron was magic, an earth angel. Over the last six years, since he was only 14, Cameron talked me down from countless ledges, talked me through eating disorders, helped me out of a dark relationship and through endless breakdowns," she emotionally said. "He would whisper the dance moves to me on live television when I didn't know what I was doing, or hold my hand quietly to communicate wordlessly when we both knew we were thinking the same thing. I can't count on my hands the number of times we ruined something because we couldn't stop making each other laugh."
"Everyone keeps talking about how talented he was, and he was undoubtedly the most talented person most of us will ever know. But what was special about Cameron was who he was in the small moments, when maybe no one was looking. The moments in between the big ones, when he didn't have to be good or kind. Cameron was always good and kind. He was selfless and generous. He was magnanimous, and inarguably a true philanthropist at only 20, beloved by anyone who had ever been lucky enough to experience his light and indescribable energy. Cameron was the ultimate example of a human being."
See more of Cameron's tribute in the video below.