Former WBO heavyweight champion Tommy Morrison passed away on Sunday evening at the age of 44.

ESPN’s Elizabeth Merrill first reported the news on Monday afternoon, noting that the once-great boxer died in a hospital in Omaha, Neb.

Morrison was diagnosed with HIV during his prime, with the announcement coming back in 1996—just before a fight with Arthur Weathers.

The Arkansas-born, Oklahoma-raised fighter, nicknamed “The Duke,” initially accepted that he contracted the disease due to his “permissive, fast and reckless lifestyle” and entered an early retirement, vowing to never fight again.

However, Morrison re-emerged in 2006, boldly claiming that he was free of the disease and speculating that HIV was a government conspiracy. He also believed his initial test was either a false positive or a dastardly ploy by a rival promoter.

He would attempt to fight after claiming to be HIV-free but could not find a bout sanctioned by a respectable commission. He beat John Castle in 2007 and defeated Matt Weishaar in 2008, but both seemed to be nothing more than publicity stunts.

Prior to his years of HIV denial, drug use, trouble with the law and health problems, Morrison had a lot going for him.

He took the WBO title from George Foreman in a unanimous decision in 1993 but lost it later that year to Michael Bentt. Morrison also appeared as “Tommy Gunn” alongside movie star Sylvester Stallone in Rocky V in 1990.

The cause of his death is currently unknown and may be a cause of contention for quite some time. According to Merrill, longtime promoter Tony Holden said, "I don't know what the official cause of death at the hospital will be. You prepare for things like this, and still you feel like you got hit by a truck when you hear the news.”

Morrison’s wife, Trisha, insisted that her husband was suffering from Guillain-Barre syndrome and not HIV.