Green Day's front man Billie Joe Armstrong is entering rehab for substance abuse.

The news comes just two days after Armstrong went ballistic in Vegas during a performance at the iHeart Radio Music Festival. He was videotaped screaming obscenities, slamming Justin Bieber and violently smashing his guitar on-stage.

The band's rep issued this statement:  "Green Day wants to apologize to those they offended at the iHeartRadio Festival in Las Vegas."

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