When the four delivery workers found the woman in the middle of the road, she was covered in so much blood that they couldn’t tell the colour of her hair.

Whoever had done this to her, authorities said later, had stabbed 19-year-old Lizette Andrea Cuesta repeatedly, then thrown her out of a car near a remote, hilly road north of San Jose, leaving her for dead.

But she wasn’t.

“Her internal fortitude, to stay alive and to fight, is pretty remarkable,” Sgt. Ray Kelly of the Alameda County Sheriff’s Office told the San Francisco Chronicle. “This young woman clung to life when she was left for dead and was able to live for another couple hours and get us that information. Ultimately that led us to these arrests.”

Authorities identified the victim, a resident of Tracy, Calif., on Tuesday evening.

They also announced the arrests of Melissa Leonardo, 25, and Daniel Gross, 19. The suspects, both from Modesto, were arrested on charges of murder and will be arraigned Wednesday afternoon.

Authorities have not released any information on a possible motive, but they said Cuesta was a friend of the suspects, who are apparently engaged.

Kelly, the sheriff’s sergeant, told reporters that Cuesta had willingly gotten into a car with Gross and Leonardo.

Investigators, he said, are still trying to determine what happened after that — and why.

After she was brutally stabbed, Cuesta had crawled nearly 100 metres — the length of a football field — to get to the road, where she had some chance of being seen by people in passing cars. That is where the UPS delivery workers found her.

Authorities determined the distance by measuring a trail of drying blood.

“You could tell it was so bad to where you just had to give her comfort,” Richard Loadholt, one of the UPS employees who had been riding with three other men on Tesla Road in Livermore around 2 a.m., told Sacramento Fox affiliate KTXL. Initially, he said he and his workmates thought she was missing an arm. “She fought like a soldier. Like a warrior.”

The hilly, winding road where she was found is a popular alternative to Interstate 580 for people travelling between Livermore and Tracy, according to Bay Area news station KRON. It was also virtually deserted in the pre-dawn hours of Monday.

The area is so remote that the UPS workers had to send other people who had gathered at the scene to an area where there was better cellphone reception to call police.

When first responders arrived, they decided that the best option was to airlift the dying woman to a hospital with an advanced trauma centre. But as they tried to save her, investigators asked her questions. The most important one: Who did this?

“I’ve been around a long time, and I can only think of two to three times that I’m aware of in our agency that we’ve been able to get a dying declaration like that,” Kelly said.

In the legal world, a dying declaration is a statement made by someone who believes they will be dead soon. It’s an exception to the legal rule forbidding hearsay in court testimony, and it can hold tremendous sway in a case.

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In this one, it led to arrests just a few hours after the woman was declared dead.

About 10 a.m. Monday, the two suspects were arrested at a home in Modesto, about an hour from where the woman had been found.

“We were able to act on the information from our victim,” Kelly said.

The sheriff’s sergeant told the Modesto Bee that investigators recovered a “tremendous” amount of evidence at the home, thanks to Cuesta’s dying declaration.