James Sikking, who starred as a hardened police lieutenant on “Hill Street Blues” and as the titular character’s kindhearted dad on “Doogie Howser, M.D.,” has died at 90.

Sikking died of complications from dementia, his publicist Cynthia Snyder said in a statement Sunday evening.

Born the youngest of five children on March 5, 1934 in Los Angeles, his early acting ventures included an uncredited part in Roger Corman’s “Five Guns West” and a bit role in an episode of “Perry Mason.” He also secured guest spots in a litany of popular 1970s television series, from the action-packed “Mission: Impossible,” “M.A.S.H.” “The F.B.I.,” “The Rockford Files,” “Hawaii Five-O” and “Charlie’s Angels” to “Eight is Enough” and “Little House on the Prairie.”

Breakthrough with ‘Hill Street Blues’

“Hill Street Blues” would debut in 1981, a fresh take on the traditional police procedural. Sikking played Lt. Howard Hunter, a clean-cut Vietnam War veteran who headed the Emergency Action Team of the Metropolitan Police Department in a never-named city.

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The acclaimed show was a drama, but Sikking’s character’s uptight nature and quirks were often used to comic effect. Sikking based his performance on a drill instructor he’d had at basic training when military service cut through his time at the University of California, Los Angeles, from which he graduated in 1959.

“The drill instructor looked like he had steel for hair and his uniform had so much starch in it, you knew it would sit in the corner when he took it off in the barracks,” he told The Fresno Bee in 2014, when he did a series of interviews with various publications marking the box set’s release.

Struggles and Success

When it debuted on the heels of a Hollywood dual strike, the NBC show was met with low ratings and little fanfare. But the struggling network kept it on the air: “Up popped this word ‘demographic,’” Sikking told the Star Tribune in 2014. “We were reaching people with a certain education and (who) made a certain kind of money. They called it the ‘Esquire audience.’”

The show ultimately ran until 1987, although for a brief moment it wasn’t clear Sikking would make it that far. A December 1983 episode ended with his character contemplating dying by suicide. The cliffhanger drew comparisons to the “Who shot J.R.?” mystery from “Dallas” not long before — although it was quickly resolved when TV supplements accidentally ran a teaser summary that made it clear Hunter had been saved.

“I remember when Howard tried to kill himself. My brother called and asked, ‘You still got a job?’ I said, ‘Yeah,’ and he said, ‘Oh good,’ and then hung up,” Sikking told The Fresno Bee.

Sikking would earn an Emmy nomination for outstanding supporting actor in a drama in 1984. The look and format of “Hill Street Blues” were something new to Sikking — and many in the audience, from the grimy look of the set to the multiple storylines that often kept actors working in the background, even when they didn’t have lines in the scene.

“It was a lot of hard work, but everybody loved it and that shows. When you have the people who are involved in the creation, manufacture — whatever you want to call it — who are really into it and enjoy doing it, you’re going to get a good product,” he told Parade.com in 2014. “We always had three different stories running through (each episode), which means you had to listen and you had to pay attention because everything was important.”

Later Career and Personal Life

Aside from “Hill Street Blues,” Sikking played Captain Styles in 1984’s “Star Trek III: The Search for Spock.” He wasn’t enthusiastic about the role, but had been lured by the idea that it would take just a day on set.

“It was not my cup of tea. I was not into that kind of outer space business. I had an arrogant point of view in those days. I wanted to do real theater. I wanted to do serious shows, not something about somebody’s imagination of what outer space was going to be like,” Sikking explained to startrek.com in 2014. “So I had a silly prejudice against it, which is bizarre because I’ve probably and happily signed more this, that or the other thing of ‘Star Trek’ than I have anything of all the other work I’ve done.”

After the end of “Hill Street Blues,” he acted in nearly 100 episodes of “Dougie Howser, M.D.,” reuniting with Steven Bochco, who co-created both “Hill Street Blues” and the Neil Patrick Harris-starring sitcom.

He married Florine Caplan, with whom he had two children and four grandchildren.

Sikking had all but retired by the time the box set of “Hill Street Blues” came out. He had fewer but memorable roles after the turn of the millennium, guest-starring on “Curb Your Enthusiasm” and acting in the rom-com films “Fever Pitch” and “Made of Honor.” His last roles were as a guest star on a 2012 episode of “The Closer” and in a movie that same year, “Just an American.”

Sikking continued to do charity events. He was a longtime participant in celebrity golf tournaments and even once made it to the ribbon-cutting for a health center in an Iowa town of just 7,200 people. “Actually, I came to get something from you — air I can’t see,” Sikking told the crowd of 100 people. “Where we’re from, if it isn’t brown, we don’t know how to breathe it, The Associated Press reported in 1982.

“I probably would do something if it got me going. Acting is a license to do self-investigation. It’s a great ego trip to be an actor,” he told startrek.com in 2014. “I must say that, in the past few years in which I haven’t worked, the obscurity has been quite attractive.”

“The condiment of my life is good fortune,” he finished.