article: More than a dozen people were injured on Thursday night after a stage collapsed during an Indiana public high school theater performance, sending students plummeting 10 feet into an orchestra pit. One of the victims suffered critical head trauma as the stage fell half-way through a song during a sold-out showing of American Pie at Westfield High School. The calamity occurred at the worst possible time - just as dozens walked on stage for the finale. 'All of a sudden, everyone was gone,' one parent from the audience told RTV. Terrible: Tragedy struck Thursday night at an Indiana high school's performance of the musical American Pie . Buckled: Just as the entire cast danced on-stage for the finale, the platform beneath them collapsed . Shocking: The performers plummeted through the wooden riser in a spectacle so unbelievable that some audience members initially believed it was choreographed . Nicola Gruszka, a student who was singing in front of the stage when the platform behind her gave way, said they had previously practiced the song with the same number of people with no issue. 'We thought the worse thing that could happen on that song is that someone could miss their cue,' she told Good Morning America on Friday. After the students behind her plunged into the orchestra pit, she was so shocked that she was unable to move, she said, and was still holding the microphone 30 minutes later. Another student, Sam Greathouse, told GMA that he jumped into action. 'As soon as the stage went down I just hopped up and started pulling people out of the hole,' he said, adding that students 'really came together as a unit in that moment'. More than 12 people were hurt and least one person was critically injured, a spokesman for the Westfield Police Department said on Thursday evening. But the two students told GMA that they had heard the critically-injured student was doing much better by Friday. 'The worst ones are comparatively mild to what could've happened,' Miss Gruszka said. Some performers walked out of the pit, which was estimated to measure some 10 feet, but others required more serious medical care . The packed house, seen before the tragedy, was asked to keep calm during the confusing aftermath . The drop from the top of the wooden riser to the floor was likely around 10 feet. Many of the witnesses who'd never seen the show weren't initially sure if it was part of the performance. The confusion didn't last, however, as it soon became clear that a terrible accident had occurred. Screams and gasps can be heard in video taken of the incident, which shows all but the lead singer vanish in the middle of the song Don't Stop Believin'. 'Some parents rushed the stage area,' audience member Mandi McKinley Brown told IndyStar. 'Most of us stayed in our seats to stay out of the way. People were lifting large pieces of the stage out of the pit from on top of the kids.' According to student Zach Rader, an administrator then addressed the crowd and asked for calm before asking any healthcare professionals to come forward. Witnesses: Nicola Gruszka, left, was singing in front of the stage when it collapsed behind her, while Sam Greathouse, right, helped to pull students out of the hole. They appeared on GMA on Friday morning . 'We have some seriously injured people,' Westfield fire chief Joe Lyons. The musical's lead guitarist, Blake Camden, was not among them. He said he stepped away after noticing something about the stage wasn't right. 'When all the performers rushed the stage, I saw the floor was starting to bow a little bit and I stepped to the left and the stage collapsed,' Camden, a senior, told RTV. 'I saw 20-30 of my friends fall in.' Chris Baldwin, who works in human resources for the high school about 20 miles north of Indianapolis, said the students fell into the orchestra pit below. Cameron Snyder, 18, a senior at Westfield, was watching the show. When the stage collapsed, a mass of people ran toward it, trying to help their loved ones, Snyder said. Scene: The incident occurred at Westfield High School, pictured on Friday as students head back to class . Back to school: Police said on Friday that the dozen students hurt in the collapse are 'doing really well' 'I was just in a state of shock,' he said. Injured students were taken to at least three different hospitals, Hollowell said. School officials aid class would be held as usual on Friday but that counselors would be on site for students who might need counseling. The incident evoked memories of a 2011 stage collapse at the Indiana Stage Fair that killed seven people and injured nearly 100. High winds toppled rigging and sent the stage roof onto fans awaiting the start of a concert by the country duo Sugarland.
highlights: An Indiana public school performance of American Pie ended in tragedy Wednesday when a riser buckled just as dozens danced on-stage .
  More than a dozen people were injured at the Westfield High performance and one student was taken to a hospital in critical condition .
  Students said there had been no issues when they previously practiced the song on the stage with the same number of people .
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