One former co-star of Bruce Willis, The Sixth Sense's Haley Joel Osment, shared an especially moving tribute to the famed actor, who was recently announced to be retiring due to an aphasia diagnosis.

Osment posted an old photo of Willis to his Instagram and added a paragraph of heartfelt reflection, saying, "It’s been difficult to find the right words for someone I’ve always looked up to—first on the big screen, and then by some wild stroke of luck, in person. He’s a true legend who has enriched all of our lives with a singular career that spans nearly half a century."

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On Wednesday, Willis' family released a statement on social media explaining that he had been diagnosed with aphasia, and that he would step away from acting. Aphasia is a disorder that impairs a person's grasp of language and ability to communicate, and the post stated that Willis' condition "is impacting his cognitive abilities." This was the first public acknowledgment of any health concerns, but some filmmakers and crew members on a number of film sets over the past few years reported noticing differences in Willis' behavior.

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The Sixth Sense, released in 1999, was the first major hit for director M. Night Shyamalan. In the paranormal thriller, Osment plays Cole, a boy with the ability to see and communicate with ghosts. The "gift" causes him a great deal of fear and trauma, but he begins to accept it after being mentored by Willis' character, Malcolm, who is suffering from an unexplained estrangement from the world. The movie was lauded for its effective use of a major twist -- revealing near the end that Malcolm himself is a ghost -- and for the performances of both Osment and Willis.

Although Osment didn't refer to the movie by title in his post, he expressed gratitude "for what I got to witness firsthand," from Willis, and ended with a message of hope for the actor and his family "as they move forward with the courage and high spirits that have always defined them."

Willis, who is now 67, has had a storied career as an action film hero. The centerpiece of his filmography is generally considered the Die Hard series, in which he played the unflinchingly resilient John McClane, but he is also known for major stand-alone hits, including The Sixth Sense as well as Armageddon, Pulp Fiction, Unbreakable and The Fifth Element.

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Source: Instagram