Stuart Margolin, the actor best known for his role as Evelyn “Angel” Martin on the 1970s detective drama The Rockford Files, has died. He was 82.

Margolin, who won two Emmy Awards for his performance on the show, passed away Monday, according to an Instagram post from his actor stepson Max Martini.

Another of his stepchildren, director Christopher Martini, said Margolin died of natural causes in Staunton, Virginia, The Hollywood Reporter reported.

“The two most profound moments in my life… the birth of my kids and being bedside as my step-father passed this morning,” Max wrote in his post Monday, along with a black and white photo of Margolin. “Love you Stuart Margolin,” he added. “A great actor/writer/producer/director. But more importantly, a profoundly gifted step-father that was always there with love and support for his family. RIP Pappy. Keep ’em cold.”

On The Rockford Files, Margolin played a lovable rogue who befriended Jim Rockford—played by James Garner—in prison. He also starred alongside Garner in the early 1970s Western Nichols, which ran for one season, and another Western, Bret Maverick, in 1981-82.

Margolin’s career began in the 1960s in appearances on shows including The Fugitive and The Monkees. He would later appear in episodes of M*A*S*H and Magnum P.I. He also starred opposite Charles Bronson in the Michael Winner movies The Stone Killer (1973) and Death Wish (1974).

Alongside his acting credits, Margolin also directed TV shows—including episodes of The Rockford Files—and the 1984 crime drama film The Glitter Dome. More recently, he appeared on screen in 30 Rock and had a guest spot as Dr. They in a 2018 episode of the revived sci-fi series The X-Files.

“I confess I’ve never understood why Rockford likes Angel so much, because he’s rotten to the core,” James Garner wrote in his 2011 memoir, The Garner Files. “But there’s something lovable about him. I don’t know what it is, but it’s all Stuart’s doing.”