We assumed rolling out a triple album and dual documentaries would be grueling stuff, but maybe not this heavy: 40-year-old Green Day front man Billie Joe Armstrong is heading to rehab for substance abuse following an onstage blowup at the iHeartRadio Music Festival in Las Vegas on Friday. Informed by a teleprompter that the band had just one minute left (several sources say that it was a surprise to the band and that they'd been shorted from 45 minutes to about a half-hour to accommodate a longer set by Usher), Armstrong stopped midway through a song and started up an F-bombed screed ("I’m not fucking Justin Bieber, you motherfuckers! You gotta be fucking joking!") concluding with a spirited guitar-smashing. Now a rep tells TMZ the band apologizes to its fans and will be canceling some upcoming promotional appearances.