Rickman played the role of Severus Snape, Hogwarts' adversarial potions master, in the eight Harry Potter movie adaptations.
"My thoughts are with [Rickman's wife Rima Horton] and the rest of Alan's family," Rowling tweeted Thursday morning. "We have all lost a great talent. They have lost part of their hearts."
There are no words to express how shocked and devastated I am to hear of Alan Rickman's death. He was a magnificent actor & a wonderful man.— J.K. Rowling (@jk_rowling) January 14, 2016
My thoughts are with Rima and the rest of Alan's family. We have all lost a great talent. They have lost part of their hearts.— J.K. Rowling (@jk_rowling) January 14, 2016
Radcliffe recalled his experience working with Rickman on the Harry Potter series.
"As an actor he was one of the first of the adults on Potter to treat me like a peer rather than a child," Radcliffe wrote in a post on Google+. "Working with him at such a formative age was incredibly important and I will carry the lessons he taught me for the rest of my life and career. Film sets and theatre stages are all far poorer for the loss of this great actor and man."
Rickman's death was confirmed Thursday morning, following his battle with cancer. He was 69.