Mariska Hargitay and other Law & Order: Special Victims Unit cast members are mourning one of their own.

Richard Belzer, who played detective John Munch on the NBC series for 15 full seasons after originating the role on Homicide: Life on the Street, died Feb. 19. The actor, who was also a standup comedian and author of conspiracy theory books, was 78.

"Goodbye my dear, dear friend," Mariska, who plays Olivia Benson on Law & Order: SVU, wrote on her Instagram. "I will miss you, your unique light, and your singular take on this strange world."

The actress continued, "I feel blessed to have known you and adored you and worked with you, side by side, for so many years. How lucky the angels are to have you. I can hear them laughing already. I love you so very much, now and forever."

Christopher Meloni, who plays Elliot Stabler on Law & Order: SVU, also paid tribute to Belzer on social media. The actor tweeted a photo of himself kissing his late co-star's cheek at the comic's 2001 Friars Club Roast, with Hargitay smiling behind them.

"Good bye mon ami," Meloni wrote. "I love you. #TheBelz."

Meanwhile, Dean Winters, who played Munch's partner Brian Cassidy on Law & Order: SVU, shared a cast photo of himself and Belzer on Instagram.

"Richard Belzer was my brother," Winters wrote. "We became fast friends in '92 when I was a bartender, faster friends when I did my first job on NBC's HOMICIDE: LIFE ON THE STREET and in 1998 he called me and said 'baby, Dick Wolf is doing a new show called LAW and ORDER SVU and he wants me to be on it. I told Dick 'Only if you make Dean Winters my partner, Brian Cassidy' Baby, are you in?' I was in."

Winters added, "There aren't a lot of people with class like that left. 'Classe non e acqua' Everyone can have water, not everyone can have class. Richard Belzer had class for days. I will miss this man very much."

Ice-T, who plays Fin Tutuola on Law & Order: SVU, also shared a tribute to Belzer on Instagram. The star, who was honored with a star on the Hollywood Walk of Fame Feb. 17, posted a cast photo of himself with the late actor, writing, "Highs and Lows… After one of the most amazing weeks of my life. I wake up to the news I lost my friend today."

Ice-T continued, "Belz is gone.. Damn it! But remember this..'When you ARE having real fun and are Truly Happy. ENJOY it to the fullest! Cause Pain is inevitably coming.' I'll miss you Homie."