Sheehan was in town with U2 as the band kicked off their week-long concerts at The Forum, reported Ace Showbiz.
Paramedics were called to his hotel room around 5:30 AM for a suspected cardiac arrest. The manager who was in his late 60s was pronounced dead on the scene.
Craig Harvey, a spokesman for the Los Angeles County coroner's office, said Sheehan possibly died of natural causes. Homicide investigators were looking into his death, said Sgt Kevin Rasmussen of the Los Angeles County Sheriff's Department.
Sheehan had worked with the band since 1982. He also helped with solo projects including Bono's appearance before Congress to raise awareness for more aid to Africa.
Outside the group, he worked with Led Zeppelin, Iggy Pop, Patti Smith, and Lou Reed. In 2008, he was feted with Parnelli Lifetime Achievement Award.