Visitor Dan Mosqueda of Colorado Springs, Colo., said the 31-year-old acrobatic performer was being hoisted up the side of the stage when it appeared that she slipped free of her safety wire and plummeted to an open pit below the stage.
"Initially, a lot of people in the audience thought it was part of the (show)," he told the Sun. "But you could hear screaming, then groaning, and we could hear a female artist crying from the stage."
The show momentarily continued, then stopped. Minutes after the accident, a recorded announcement informed audience members that refunds or vouchers to future shows would be offered, and the crowd was dismissed.
Cirque du Soleil founder Guy Laliberte issued a statement Sunday praising Guyard-Guillot and saying performances of "Ka" have been canceled until further notice.
Guyard-Guillot, a mother of two children, had been with the original cast of "Ka" since 2006, and had been an acrobatic performer for over 20 years.
"I am heartbroken. I wish to extend my sincerest sympathies to the family. We are all completely devastated," Laliberte said. "We are reminded with great humility and respect how extraordinary our artists are each and every night. Our focus now is to support each other as a family."
Cirque officials are working with authorities investigating the accident and have offered their full cooperation, he added.
The Clark County Coroner's Office will rule on the cause of death.