U2's tour manager Dennis Sheehan has been found dead at a hotel in southern California, a day after the rockers kicked off a five-night stint in the Los Angeles area.
U2 frontman Bono posted a statement on the band's website about Mr Sheehan's death.
"We've lost a family member, we're still taking it in," Bono wrote. "He wasn't just a legend in the music business, he was a legend in our band. He is irreplaceable."
Mr Sheehan died at the Sunset Marquis Hotel in West Hollywood. He has managed U2's tours for more than three decades.
Los Angeles County Fire Inspector Chris Reade said first responders were called at around 5.30am local time to reports of a man in cardiac arrest. Mr Sheehan was pronounced dead at the scene. Coroner's investigators are at the hotel.
The Irish quartet brought their Innocence & Experience tour to The Forum in Inglewood on Tuesday, the first of five nights in the Los Angeles area. Launched earlier this month in Vancouver, Canada, the North American and European tour continues until November 15.
"With profound sadness we confirm that Dennis Sheehan, U2's longstanding tour manager and dear friend to us all, has passed away overnight," said Arthur Fogel, of entertainment and promotions company Live Nation. "Our heartfelt sympathy is with his wonderful family."