U2's longtime manager died early this morning, just as the band kicked off their week-long stint of concerts in LA.
Dennis Sheehan was found unconscious in his room at the Sunset Marquis Hotel.
Paramedics were called to the room at approximately 5.30am for a reported cardiac arrest.
He was pronounced dead at the scene.
Bono has paid tribute to his colleague and friend today, saying the band 'lost a family member'.
"We've lost a family member, we're still taking it in," the Irish musician wrote on the band's official website.
"He wasn't just a legend in the music business, he was a legend in our band. He is irreplaceable."
Music promoter Arthur Fogel said it is 'with profound sadness' that he confirmed Mr Sheehan's death.
"With profound sadness we confirm that Dennis Sheehan, U2's longstanding tour manager and dear friend to us all, has passed away overnight," he said.
"Our heartfelt sympathy is with his wonderful family."
Mr Sheehan, who was in his late sixties, has been U2's tour manager for the last three decades.
Born in Wolverhampton in the UK, he also worked with Led Zeppelin, Iggy Pop and Lou Reed.
He was previously awarded the Parnelli Lifetime Achievement Award in 2008 for his work in the music industry throughout four decades.
A fellow tour manager Jake Berry described Dennis at the time as 'great, hardworking and loyal who always has everyone’s best interest at heart all the time'.
Jake also recalled a time U2 dressed as members of Led Zeppelin in his honour and said 'they'd do anything for him'.
He began his long career with U2 in 1982.