"Alan Rickman is undoubtedly one of the greatest actors I will ever work with," Radcliffe, who played Harry Potter, wrote on his Google+ page. "He is also one of the loyalest and most supportive people I've ever met in the film industry. He was so encouraging of me both on set and in the years post-Potter. I'm pretty sure he came and saw everything I ever did on stage both in London and New York. He didn't have to do that. I know other people who've been friends with him for much, much longer than I have and they all say [is], 'If you call Alan, it doesn't matter where in the world he is or how busy he is with what he's doing, he'll get back to you within a day.'"
Unlike some of the "downright scary" characters Rickman portrayed onscreen, Radcliffe says that Rickman was "extremely kind, generous, self-deprecating and funny."
"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 continued. "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."
Watson's messages, posted to her Facebook and Twitter pages, echoed Radcliffe's points about Rickman's friendliness.
"I'm very sad to hear about Alan today," Watson, who starred as Hermione Granger in Harry Potter, stated. "I feel so lucky to have worked and spent time with such a special man and actor. I'll really miss our conversations. RIP Alan. We love you."
I'm very sad to hear about Alan today. I feel so lucky to have worked and spent time with such a special man and actor. I'll really miss our conversations. RIP Alan. We love you
J.K. Rowling, author of the fantasy series, also took to Twitter to honor the late actor, writing, "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."
"My thoughts are with [Rickman's wife] Rima and the rest of Alan's family," she continued. "We have all lost a great talent. They have lost part of their hearts."
Knowing that their fans were just as devastated by news of Rickman's passing, the official Harry Potter Facebook page paid tribute to him with a photo of Rickman dressed in character on set. "We are deeply saddened to hear of the passing of our beloved Alan Rickman who played Professor Severus Snape," the caption read. "Harry Potter fans will miss him very much. He was a wonderful actor and a very dear friend."
We are deeply saddened to hear of the passing of our beloved Alan Rickman who played Professor Severus Snape. Harry Potter fans will miss him very much. He was a wonderful actor and a very dear friend.
In addition to his famous role in the Harry Potter film franchise, he also starred in Die Hard, Sense and Sensibility, Love Actually and Robin Hood: Prince of Thieves. His later work included director Tim Burton's Sweeney Todd: The Demon Barber of Fleet Street and Alice in Wonderland.