Iconic actor Richard Belzer, best known for his role as Detective John Munch on Law & Order: Special Victims Unit, has passed away at age 78.

Belzer, who was born in Bridgeport, Connecticut, had a long and successful career in both film and television. He began his acting career in the 1970s and quickly became a popular comedian, appearing on Late Night with David Letterman and Saturday Night Live.

In 1993, Belzer was cast as Detective John Munch on the hit show Homicide: Life on the Street. He went on to appear in the show for nine seasons, and later reprised the role on Law & Order: Special Victims Unit, where he appeared in more than 200 episodes.

In addition to his acting career, Belzer was a passionate advocate for civil rights and social justice. He was an active member of the ACLU and was an outspoken critic of the death penalty.

His death has been met with an outpouring of grief from fans and colleagues. Belzer’s former co-star Mariska Hargitay said in a statement that “Richard was one of a kind. I am so lucky to have known him and to have learned from him. He was a master of his craft and a true artist.”

Belzer is survived by his wife, actress Harlee McBride, and his two children.