In one of the more surprising moments of the year, Green Day frontman Billie Joe Armstrong recently entered rehab for substance abuse problems, and now Green Day bassist Mike Dirnt has just addressed the issue in greater detail.

After slinging curses at the iHeart Radio festival organizers, Armstrong smashed his guitar and left the stage. At the time, the singular reason for his outburst seemed to be frustration with having Green Day's set time suddenly cut down by 20 minutes. The next day, though, it was revealed that there was more to Armstrong's breakdown, as the band released a statement that the frontman would be entering rehab.

In an interview with BBC Radio 1 [via NME], Mike Dirnt revealed that the decision to send Armstrong to rehab wasn't a difficult one, "We had to put the life of our friend in front of everything," says Dirnt. There were also "signs of things hitting the fan" adding, "we hadn't slept in forever."

Dirnt continues, “Hindsight is 20/20… it was a tremendous undertaking… It catches up with you a little bit. We definitely jumped off a moving train." As for the future of Green Day's musical career, Durst says, "We’re still getting ready for the next phase."

Stay tuned for more news on Billie Joe Armstrong's recovery. In the meantime. the band recently released the album '¡Uno!,' with the rest of the trilogy coming in the forms of  '¡Dos!' next month and '¡Tre!' in January. In addition, Armstrong's previously taped appearances as a mentor on NBC's 'The Voice' will begin airing tonight (Oct. 8) on NBC.