(CNN) -- Tragedy struck at a Pennsylvania circus Friday after a startled elephant stomped its trainer to death, police said.

People at the Irem Shrine in Wilkes-Barre, which has been hosting the James Hamid Circus all week, rushed to help but not before the trainer sustained life-threatening injuries, said police Lt. Steven Oshefski.

It was unclear what spooked the elephant, but the pachyderm was calmed by those on the scene.

The victim is not being identified until next-of-kin have been notified, Oshefski said.

The incident was classified as a workplace accident and the investigation has been turned over to the Occupational Safety and Health Administration.

A balloon vendor at the circus told CNN affiliate WBRE that the death was shocking.

"In the 30 years I've been doing my vending, I've never heard an animal killing their trainer and all," said Ed Conrad. "So something must have happened."

Oshefski said the elephant came into contact with electrical wires, but it was unclear what exactly startled the animal.

Animal rights activists decried the use of animals in circuses.

"It should come as no surprise that elephants and other animals sometimes snap and attack circus employees and members of the public," said Robbyn Brooks of the People for the Ethical Treatment of Animals (PETA).

"PETA has obtained shocking photos and video of circus trainers as they beat elephants and subject them to violent training methods using barbaric devices such as bullhooks," Brooks said.

Circus members observed a moment of silence for the elephant handler who died, WBRE reported. The circus, however, made a decision almost immediately after the death that the performance would go on.