John Aylward, best known for his roles in the medical drama "ER" and "The West Wing" has died at 75.

Aylward died at his Seattle home on Monday due to natural causes, his long-time friend and agent, Mitchell Stubbs, shared with Fox News Digital. He was first alerted to the news by the actor’s wife, Mary Fields.

"John was a wonderful actor and a great friend to many. He was proud of his film and television work, although his life in the theatre was where he was the happiest," Stubbs shared. "He was a good man."

John Aylward

John Aylward has died at 75 due to natural causes. (Photo by Walter McBride/Getty Images)

Aylward was a graduate of the University of Washington’s actor’s training program in 1970 and went on to form the Acting Space Theatre in 1973. 

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His first on-screen gig was for the 1976 movie "The Secret Life of John Chapman." 

John Aylward in "ER"

John Aylward as Doctor Donald Anspaugh in the medical drama "ER." (Photo by Chuck Hodes/NBCU Photo Bank)

Aylward didn’t have a breakthrough for nearly 20 years. He’s most famously known for his role in the medical drama "ER" as Dr. Donald Anspaugh. Until he landed this role, Aylward primarily worked in theater. 

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The late-actor also portrayed the character former DNC chairman Barry Goodwin on "The West Wing." Other television roles include "American Horror Story," Yoon which he played Father Malachi. 

John Aylward in "The West Wing"

(L-R) Allison Janney as Claudia Jean 'C.J.' Cregg, John Aylward as Barry Goodwin Former DNC Chair and Bradley Whitford as Josh Lyman in "The West Wing." (Photo by Mitch Haddad/NBCU Photo Bank)

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Aylward is survived by his wife, Mary Fields.