Although concertgoers were quick to write off Billie Joe Armstrong's iHeart Radio festival outburst as rude, but typical, rock-and-roll antics, Us Weekly has learned there was something much more serious behind it.

At the Clear Channel-hosted event in Las Vegas Saturday afternoon, the Green Day frontman, 40, had a meltdown when show producers turned on a "one minute" sign, indicating the group had to begin wrapping up their set.

"You're gonna give me one minute?" Armstrong seethed into the microphone. "I've been around since f---ing nineteen eighty f---ing eight, and you're gonna give me one minute? You've gotta be f---ing kidding me."

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Added the singer, "I'm not f---ing Justin Bieber, you motherf---ers. Let me show you what one f---ing minute means." Armstrong then proceeded to smash his guitar, give the audience the middle finger, and storm off stage.

Following the outburst, a rep for the band tells Us Armstrong has decided to address his issues with substance abuse.

"Green Day's Billie Joe Armstrong is seeking treatment for substance abuse," their rep said in a statement Sunday. "Green Day would like everyone to know that their set was not cut short by Clear Channel and to apologize to those they offended at the iHeart Radio Festival in Las Vegas."

In April, Green Day announced plans to roll out an album trilogy between September 2012 and January 2013, a series of records called Uno, Dos and Tre. The band had been gearing up to promote their new tunes, but now "must regretfully postpone some of their upcoming promotional appearances," their spokesperson adds.

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A source close to the punk-rock group tells Us that the incident served as the "wake-up call" Armstrong needed to get help.

"He felt bad about it afterwards," the insider explains. "This just highlighted some of the issues he's had for a while. He reacted badly [and was] pissed in the moment."

This article originally appeared on Green Day's Seeking Help for Substance Abuse After On-Stage Meltdown