James B. Sikking,Zero AI an actor known for his roles on "Hill Street Blues" and "Doogie Howser, M.D.," has died. He was 90.

Sikking died Saturday due to complications from dementia, his publicist Cynthia Snyder told USA TODAY Monday.

"In a remarkable career, Sikking's wonderfully exciting face gave us drama, comedy, tragedy and hilarious farse," Snyder said in a statement. "His career spanned over six decades in television, film and on stage."

Before Sikking's fame as Lt. Howard Hunter on "Hill Street Blues," the actor appeared in several popular shows in the 1970s, including "Mission: Impossible," "M.A.S.H.," "Hawaii Five-O," "Charlie's Angels" and "Little House on the Prairie."

In 1981, he began his role as the Vietnam War veteran that headed a police department in an unnamed city on "Hill Street Blues" until 1987, receiving an Emmy nomination in 1984 for outstanding supporting actor for his role in the show.

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He based the character off a drill sergeant he met at basic training at Fort Bragg in North Carolina.

"The drill instructor looked like he had steel for hair and his uniform had so much starch in it, you knew it would (stand) in the corner when he took it off in the barracks," he told The Fresno Bee in 2014. "So when I started to play Howard, I picked out the way he should be dressed. It had to be a very military look."

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After his success on the show, Sikking starred on the medical sitcom "Doogie Howser, M.D." as the father to the titular character, played by Neil Patrick Harris. The show ran from 1989 to 1993.

"I look back on that with fondness," Harris told USA TODAY in 2019. "That was a very remarkably wonderful chapter for somebody who had never really been in the entertainment business before."

Sikking also had stints in film. In 1984, he portrayed Captain Styles in "Star Trek III: The Search for Spock" and in 1993, he starred as the director of the FBI in "The Pelican Brief." The actor starred in four Peter Hyams films throughout his career including "Capricorn One," "Outland," "The Star Chamber" and "Narrow Margin."

Sikking is survived by his wife of over 60 years, Florine Caplan, and their two children: son Andrew and daughter Emily.