The Black Sabbath bassist shared details of Osbourne’s final performance, including how “frail” he had become, in an essay for the Sunday Times. Butler said the iconic rocker needed the assistance of three people while rehearsing and had to sit down while he sang.

The Prince of Darkness, who died Tuesday at age 76, was photographed publicly for the last time at his Black Sabbath farewell concert in Birmingham, England on July 5. The rocker took the stage in front of the 42,000-person crowd at Villa Park for what turned out to be his last performance in his lifetime.