Belzer was one of the few actors I can think of who transferred his character from one TV show - "Homicide: Life On The Street" - to another - "Law & Order: SVU." His sardonic and long-suffering Lt. Munch was a major part of both series. He was 78. 

In fact, the linked article indicates the character actually appeared on 11 different series over the years, including "The X-Files." A real rarity and a funny man. 

Richard Belzer Dead at 78: 'Law & Order: SVU' Actor's Colleagues Confirm His Passing