Farewell, Sgt. John Munch. Law & Order: Special Victims Unit fans were thrown for a loop on the Wednesday, Oct. 9 episode of NBC's hit, but it wasn't just because of the drama's intense cop-rape storyline. After 15 seasons, it was revealed that beloved SVU mainstay Richard Belzer (Sgt. John Munch) would leave the series as a full-time costar.

"Munch put in his papers," Dann Florek's Capt. Cragen told a stunned Olivia Benson (Mariska Hargitay) at the conclusion of the Oct. 9 episode, which featured Benson's live-in boyfriend Brian Cassidy (Dean Winters) going undercover to investigate a series of alleged rapes committed by members of the NYPD. "Liv, it's OK. Nothing changes. Except what has to."

Originating the role of John Munch in 1993 on NBC's Homicide: Life on the Street, actor, author and comedian Belzer, 69, went on to appear on the SVU version of Dick Wolf's franchise in more than 320 episodes. His cop character also popped up in episodes of The X Files, The Beat, Law & Order and Law & Order: Trial By Jury, among other TV series.

Though SVU's fictional 16th precinct will fete the beloved sergeant in a retirement party episode on Oct. 16, a source tells The Huffington Post Belzer could return to the NBC series in a guest star capacity, something the actor himself would welcome. "I'd be a fool to say I didn't want to do it anymore and I'm certainly not bored with the character because the writing is so good," Belzer told The Huffington Post in May. "[Munch is] very close to how I would be if I were in that situation, so it's a dream."

Belzer is not the first high-profile member of SVU to exit the squadroom in recent years. Chris Meloni's Det. Elliot Stabler — beloved by fans as Benson's longtime partner — concluded his run on the series in 2011 after 12 seasons.

Law & Order: Special Victims Unit airs Wednesdays at 9 p.m. (EST) on NBC.