Festival organizers believe the man had an underlying medical condition.
Classic records from The Roots, R.E.M., and Steely Dan are also thought to have been destroyed in the blaze.
The band was on its way to a show in Santa Ana, California.
The band offers its deepest condolences to the fan’s family and loved ones.
Five people were seriously injured, but police said there were no known fatalities.
The band’s drum technician, Scott Johnson, lost his life in the incident.
13 people have died at Bonnaroo over the course of the festival’s 17-year history.
“We had a fairytale life and now it has turned into some sick Shakespearean tragedy.”
Billie Joe Armstrong says the band had no idea what had happened, adding, “We are not heartless people.”
The band has drawn criticism for deciding to perform as scheduled.
“I would rather get on the floor and be trampled by the parents” than answer questions, says Derick Almena.
The live-in artist commune caught fire on Friday night.