Rusted Root frontman Michael Glabicki was stricken with severe altitude sickness before his band’s show at Colorado’s Red Rocks Amphitheatre, which sits at 6,400 feet above sea level, this past weekend.

Rusted Root was scheduled to perform at “Blues Traveler’s Fourth of July at Red Rocks,” with the titular band, Spin Doctors and The Samples, but according to a pair of statements posted to Rusted Root’s Facebook page, Glabicki felt ill from the minute he arrived in Denver. His condition only worsened after performing soundcheck, and a half hour before Rusted Root was scheduled to take the stage medics were called to assess the singer’s condition.

“Within 10 minutes our dressing room turned into a full on medical facility with heart monitors, EMS, and doctors.” Glabicki wrote. “They told me that my blood pressure was so high that I was in real danger of dying.”

According to WebMD, acute altitude sickness can severely damage your lungs and brain: “Symptoms include being confused, not being able to walk straight, feeling faint, and having blue or gray lips or fingernails. When you breathe, you may hear a sound like a paper bag being crumpled.”

After Glabicki was taken to the hospital, Rusted Root percussionist/vocalist Liz Berlin took center stage and enlisted Chris Barron of Spin Doctors and John Popper of Blues Traveler to perform an impromptu set. Unfortunately, Rusted Root was already missing bassist Patrick Norman, who has been M.I.A. for the past few dates of the band’s tour.

Thankfully, Glabicki has bounced back from his illness, and Rusted Root will continue their tour as planned. You can see the band’s upcoming tour dates here.