Mike Scaccia, guitarist with heavy metal bands Ministry and Rigor Mortis, has died at the age of 47.
Rolling Stone magazine reported that he was playing at a birthday celebration for Rigor Mortis singer Bruce Corbitt when he collapsed on stage in Texas.
He was rushed to hospital, where he was pronounced dead.
Al Jourgensen, Ministry's lead singer, confirmed his death on the band's website, telling fans: "I just lost my lil' brother and my best friend."
He continued: "Mikey was not only the best guitar player in the history of music, but he was a close, close, close part of our family - and I just lost a huge chunk of my heart today.
"Our lives are forever changed. Life without Mikey is like orange juice without pulp - kind of bland."
Scaccia was born in Babylon, New York in 1965 and formed group Rigor Mortis in 1983.
Combining a savage and dense rock sound with their shared love of horror films, the band almost single-handedly created a death-metal scene in their native Texas.
Unusually, they were signed to a major label - Capitol Records - and released one album before being dropped due to poor sales.
Jourgensen invited Scaccia to join Ministry in 1989, and he played on the band's most commercially-successful album, Psalm 69: The Way to Succeed and the Way to Suck Eggs, in 1992.
He also contributed to spin-off projects by bands such as Lard and Buck Satan and the 666 Shooters, and was part of a well-received Rigor Mortis reunion in 2003.
According to the Fort Worth medical examiner, the guitarist died of a sudden heart attack brought on by a heart disease.
Rigor Mortis vocalist Corbitt paid tribute to his friend on Facebook, calling him "the greatest guitar player I ever knew".
"My brother is gone," he wrote. "The only reason I am who I am is because of this man. If it wasn't for him I wouldn't even be in a band."