Clarence Gilyard, a veteran actor who had notable roles in Die Hard, Matlock and Walker, Texas Ranger who would later become a theater professor and author, has died. He was 66.

The University of Nevada, Las Vegas College of Fine Arts, where Gilyard taught, announced his death on Monday afternoon, according to the Las Vegas Review-Journal. He had been suffering from a long illness. No further details were released.

In a rich and varied career that spanned five decades, Gilyard achieved success in film, television and on stage. For film fans, he is perhaps best known for playing Theo, Hans Gruber’s cocky tech whiz in 1988’s Die Hard. In the 1990s, Gilyard was a familiar face on primetime television, first as private investigator Conrad McMasters on the legal drama Matlock and then, in a career-defining role, as Ranger James Trivette in the long-running series Walker, Texas Ranger.

More to come…