(CNN) John Aylward, a veteran film and television actor for more than three decades, has died, according to his longtime agent and friend, Mitchell K. Stubbs.
He was 75.
Aylward died Monday of natural causes, Stubbs told CNN.
"He was a wonderful actor and a phenomenal human being," Stubbs said.
Alyward, a Seattle native, was best known for playing the stern but fair Dr. Donald Anspaugh on NBC's "ER" and Barry Goodwin on "The West Wing."
Aylward graduated from the University of Washington School of Drama in 1971, according to the school's website. He worked mostly in theater for 15 years before moving onto work on the small and big screen, the site also says.
Among his first credits is a recurring role on "Northern Exposure." Other work included roles on shows like "Family Law," "The Practice" and "Mad Men."
Aylward appeared in more than 70 episodes of "ER" over the show's 15 seasons. Through that, especially at the height of the show's popularity, when it would regularly notch roughly 30 million viewers per week, Aylward became a highly recognizable face.
In an interview with the Seattle Times around the time the show ended, Aylward describe the investment fans had in the show.
"When I was doing "Death of a Salesman" at ACT (in 1998), I was still appearing frequently on 'ER,' and it was right after the season in which Anspaugh's son had died. It was a Monday (off-day for theater actors), and I was in the checkout line at the grocery store, and this woman came running up to me and said, 'Excuse me, I'm sorry to bother you, I've been out of the country ... what happened to your son?' A'd I said, 'Oh, he died,'" Aylward told the newspaper. "The lady says 'Oh, no!' and I said, 'Yeah, we buried his ass last week!" and the girl checking out the groceries turned as white as a sheet, so I had to stop and say, 'We're talking about a TV show!' I could tell she was thinking 'Who is this heinous man who talks about the death of his kid like that.'"
Roles in the TV shows "Briarpatch" and "Yellowstone" were among Alyward's final credits.