Updated

An Australian twin who survived a suicide pact with her sister told authorities during emotional questioning that they were trying to carry out the plan at a state park shooting range but would not explain why they wanted to die.

"She was angry, upset, frustrated — any of the range of emotions one must feel," Arapahoe County Sheriff's Capt. Louie Perea said Thursday of the surviving sister.

Each 29-year-old woman shot herself in the head with ammunition bought at Family Shooting Center, investigators said, with one twin using a rented .22-caliber revolver and the other a rented .22-caliber semiautomatic handgun.

One died Monday at the range in suburban Denver. The other is recovering from a serious head wound. No suicide note was found, and investigators have said a search of the twins' luggage revealed nothing.

Authorities haven't released the names of the sisters, but an affidavit filed by deputies seeking to search their hotel and luggage identified them as Kristin and Candace Hermeler.

Arapahoe County Sheriff Grayson Robinson confirmed the accuracy of the affidavit but declined to formally release the names in deference to the family.

The document said authorities didn't know which sister had survived. Relatives were expected to arrive in Colorado on Friday.

Perea said physical evidence and surveillance video from the range supports the existence of the suicide pact.

A witness at the shooting range saw two women fall down, with one rolling around and yelling for help, the affidavit states.

An arriving deputy found one sister on her back and the other sitting on her feet. When she fell over, the officer noticed a gunshot wound to her forehead.

The sisters, who are from Australia's Victoria state, had been in the Denver area for about five weeks. One had gun training two weeks before the shooting, and both showed up at the range about a week later for additional gun training, Perea said.

On Monday, the sisters took a taxi to the range from their hotel about six miles away and rented the pistols. They took target practice on the chilly afternoon, prompting one sister to borrow a jacket, Perea said.

They initially shared a stall near a person firing a high-powered rifle. After the twins complained about the noise, range staff moved them to another lane.

"I don't know if they did that to be in a more secluded area or what," Perea said.

One of the sisters then left to place the jacket on a nearby table — apparently deciding against wearing borrowed clothing for what was to follow.

Authorities said surveillance video captured the incident. It showed the sisters falling out of the stall about a half-second apart, with other patrons quickly reacting, Perea said.

The twins had been at the range about an hour and 20 minutes.

It's not clear what they were doing in the United States.