Told he had one minute left to perform his set, Armstrong began yelling at event organizers on stage and told them "I'm not f***ing Justin Bieber" before breaking his guitar, throwing it, and storming off stage.
"Gave them eighty f***ing minutes and you're going to give me one f***ing minute," Armstrong screamed. "You gotta be f***ing kidding me. What the f***. I'm not f***ing Justin Bieber, you muthaf***ers. You've got to be f***ing joking. I got one minute. One minute left. Now I got nothing left."
Grabbing his guitar, Armstrong went on to say "let me show you what one f***ing minute, f***ing means."
After smashing his guitar on stage (see video below), Armstrong gave the audience the finger and said "One fucking minute. God f***in love you all. We'll be back" as he stormed off stage. The rest of the band followed.
Sources at the event say Armstrong snapped because other performers before him allegedly went over, including Usher. Instead of allowing the event to run behind, event organizers cut Green Day's set short.
Earlier in the show Armstrong had walked around on stage with his shirt off and no underpants, visibly showing part of his genital area.
The iHeartRadio Festival continues Saturday night in Las Vegas.