The band released a statement on their social media channels saying they were ‘heartbroken’ after Aunión Monroy fell from a cage during a stunt at the event in Madrid on Friday night.
The 42-year-old acrobat, who lived in Brighton, is believed to have fallen 30m (100 ft.) while performing in between sets by Alt-J and Green Day.
He is thought to have been wearing a harness as the box was suspended from a crane.
Paramedics spent 30 minutes trying to revive him but were unable to save him.
Green Day claimed that they were not told about the accident until after they had got off stage. They said: ‘Many of you are wondering why we continued to play our show after the accident. Green Day did not hear about the accident until after our show was over. We didn’t even know there was an acrobat performance at all. These festivals are huge.’
The band revealed they were told a ‘security issue’ had delayed their set, but weren’t told exactly what that was.
‘Everything seemed normal. The crowd and fans had a good time. We got off stage and drove back to our artist compound. It was there when we were told the shocking news about Pedro.
‘All of us were in disbelief. I don’t know why the authorities chose not to tell us about the accident before our concert.
‘If we had known prior to our performance we most likely would not have played at all. We are not heartless people. The safety and well being at any of our concerts absolutely comes first. What happened to Pedro is unthinkable.’