”Suddenly, there was a loud crash and it sounded like sheet metal and lightening and we just saw the stage collapse,” said Dusty Lalas, an employee with Toronto radio station The Edge, which was sponsoring the concert.
"The structure just caved in."
Chris Collins was heading to the show and saw the stage come down from the parking lot at Downsview Park.
"To be honest, it sounded like a roller coaster," Collins told ABC News. "Basically, like a series of clacking noises and increasing in volume as the collapse proceeded."
The stage collapsed onto workers preparing the structure for the concert, said Toronto police Const. Tony Vella.
”From my understanding, it was all stage crew, they were simply preparing for the concert,” he told reporters.
Police were not immediately releasing the identity of the dead person, who was pronounced dead at the scene by paramedics.
One other person was taken to hospital with non-life threatening injuries, another two people were treated at the scene, said Peter Rotolo a unit commander with Toronto Emergency Medical Services.
“Fortunately we had a unit that was already on the scene for the concert,” he said. ”They were on the scene immediately to render aid to the injured staff.”
It was not immediately known what caused the collapse. The weather was sunny and clear in Toronto.
Ontario Ministry of Labour investigators were at the site Saturday evening inspecting the wreckage.
The concert was cancelled, according to a tweet by the band. Radiohead's website had listed the concert as being sold out.
Police say the park wasn't full at the time of the collapse, but there was a considerable crowd of people already waiting for the show. Security at the event moved people out of the venue.
"The security team came out, huge security team it was actually very well orchestrated everyone went out without any incident," Lalas said.
There have been a number of stage collapses in recent years.
Six people died last August when the stage collapsed at a Sugarland concert in Indianapolis; five died in Belgium when a storm swept in and toppled the stage at the Pukkelpop Festival.
In Canada, several people were injured when the stage went down at Bluesfest in Ottawa last July and one person died and more than a dozen were injured in 2009 when a powerful windstorm caused the main stage to collapse at the Big Valley Jamboree near Camrose.
Also on HuffPost