Dennis Sheehan, longtime tour manager for U2 died Wednesday morning at a hotel in West Hollywood, just hours after U2 began their 5-night run at the Forum.

Sheehan, 68, was pronounced dead after firefighters responded to a call to the Sunset Marquis Hotel at 5:34 am for an apparent cardiac arrest.

While homicide investigators are reportedly looking into Sheehan’s death, a spokesman for the Los Angeles County coroner’s office said it may be attributed to natural causes.

Sheehan had worked with U2 since 1982. In addition, he worked with led Zeppelin, Lou Reed, Patti Smith and many other rock acts throughout his career.

Our condolences go out to Dennis’ friends and family.