Grammer paid a brief but touching tribute to his longtime TV father.
Kelsey Grammer is mourning the loss of his TV dad.
The Frasier star provided a brief, but heartfelt response to ET after the death of John Mahoney -- who played Martin Crane on the long-running sitcom -- at age 77.
“He was my father," Grammer, 62, said. "I loved him."
Mahoney's rep confirmed his death to ET on Monday, which happened in Chicago on Sunday "after a short illness." According to multiple reports, he was in hospice care when he died.
Mahoney earned two Emmy nominations for his role on Frasier, where his chemistry and bond with Grammer, as well as his other TV son, David Hyde Pierce's character, Niles, was unmistakable.
Mahoney also starred in such films as Say Anything and Barton Fink. Recently, he also had a recurring role on Hot in Cleveland, where he played a love interest of Betty White.
The actor was born in Lancashire, England, becoming a U.S. citizen in 1959. Before taking up theater and acting in 1977, he served in the U.S. military and worked as an English teacher at Western Illinois University. Mahoney was unmarried and never had children.
Watch the video below for more on his death.