Gilyard went on to become a theater teacher and author, and his death was confirmed in a statement released by the University of Nevada, Las Vegas (UNLV) College of Fine Arts, where he had served as the department of film professor since 2006.

“Professor Gilyard was a beacon of light and strength for everyone around him at UNLV,” said UNLV film chair Heather Addison. “Whenever we asked him how he was, he would cheerfully declare that he was ‘Blessed!’ But we are truly the ones who were blessed to be his colleagues and students for so many years.”

Fine Arts Dean Nancy Uscher said: ““His students were deeply inspired by him, as were all who knew him. He had many extraordinary talents and was extremely well-known in the university through his dedication to teaching and his professional accomplishments.”

According to the release, Gilyard had been suffering from a long illness. No further details have yet been released.

Born into a military family in Moses Lake, Washington, Gilyard moved to Los Angeles in 1979 to pursue a career in acting and landed roles on TV shows like Diff’rent Strokes and CHiPS in the years that followed.

He went on to make his big screen debut in 1986’s Top Gun, playing Lieutenant Junior Grade Marcus “Sundown” Williams and also appeared in The Karate Kid Part II. His most recognisable role came two years later with Die Hard and the part of Han Gruber’s computer hacker sidekick, Theo.

Gilyard went on to enjoy more success on the small screen with series regular roles on Matlock and alongside Chuck Norris on Walker, Texas Ranger, before embarking on a new career in academia.

Despite a host of major credits to his name, Theo in Die Hard remains his best known role, with fans flocking to Twitter to pay tribute to the man behind the iconic action movie character.

Film critic Courtney Howard wrote: “Actor Clarence Gilyard solidified his place in film history as Theo in DIE HARD (which he revived in a ‘21 Super Bowl ad) & in TV as Conrad McMasters in MATLOCK. But he also made an innumerable impact in real life as a film studies professor at UNLV. May he Rest In Peace.”

Fellow actor Chris Reed also paid tribute, describing Gilyard as a “legendary screen presence” alongside stills of the late 66-year-old in Top Gun and Die Hard.

GetFandom’s managing editor, Eric Goldman, tweeted: “He was so great in Die Hard as Theo and I always hoped they’d bring him back in a sequel (he was one of the only guys in Hans’ crew to survive!) but it was not to be. RIP, Clarence Gilyard Jr.”

Screenwriter and producer Ben Trebilcook, who previously worked on a script for an unmade Die Hard sequel, said: “Sad to learn of the passing of Professor Clarence Gilyard. A terrific actor, too, whom of course played Theo in #DieHard, a surviving character I brought back in my Die Hard 6. Sending Thoughts and prayers to his family at this time.”

Writer Lisa Hendey commented: “Just learned of the passing of Clarence Gilyard. He was a talented man with a very generous spirit. Praying for his family and loved ones.”

Tributes also came in from those Gilyard helped and influenced through his work as a university professor.

TCFontaine tweeted: “Thank you for teaching me how to ’live’. Forever my acting teacher/colleague.” Sarah O’Connell also tweeted: “This hurts. Clarence Gilyard was a centered presence in the UNLV Theatre Dept. I enjoyed several contemplative chats with him over the years. He lived a remarkable life. Peace be with his family and all who mourn him.”

Fans were also full of praise for the star and his role in shaping Die Hard as a much loved action film and holiday season favorite.

Joseph Finn tweeted: “We were already planning on watching Die Hard tonight for our annual Christmas viewing, but goodness learning of the death of Clarence Gilyard made it essential.”

Menace2Snacks meanwhile quoted one of Gilyard’s best loved lines from Die Hard, tweeting: “RIP KING CLARENCE GILYARD JR. The quarterback is toast.”

Newsweek has contacted Gilyard’s representatives for comment.