Richard Belzer, the comedian and actor who published several books over the course of his long career, has died at 78, according to the Hollywood Reporter.

Belzer, a Connecticut native, worked as a stand-up comedian and appeared in films including Scarface and Night Shift and in TV series like Lois & Clark: The New Adventures of Superman and The Flash.

He was best known for playing acerbic police detective John Munch in the series Homicide: Life on the Street, based on David Simon’s book, and Law & Order: Special Victims Unit. He played the same character in guest appearances on nine other shows, including The X-Files, Arrested Development, and The Wire.

Belzer published several books, including two novels, I Am Not a Psychic! and I Am Not a Cop!, both co-written with Michael Black. A critic for Kirkus called the latter book “a weird, surprisingly quick-witted comedic caper.”

Like Munch, Belzer was fascinated with conspiracy theories, which inspired a handful of his books including UFOs, JFK, and Elvis: Conspiracies You Don’t Have To Be Crazy To Believe and Hit List: An In-Depth Investigation Into the Mysterious Deaths of Witnesses to the JFK Assassination, the latter co-written with David Wayne.

Belzer’s admirers paid tribute to him on social media. On Twitter, comedian Laraine Newman wrote, “I loved this guy so much…One of the funniest people ever. A master at crowd work. RIP dearest.”

And actor Marlee Matlin tweeted, “Richard Belzer was one of the…kindest and welcoming actors when I guested on two episodes of Law and Order: SVU. His passing is truly a loss for Hollywood and I will miss him dearly.”

Michael Schaub, a journalist and regular contributor to NPR, lives near Austin, Texas.