Fresno County Coroner David Hadden said Dianna Hanson died instantly when the 550-pound lion broke her neck, apparently with a swipe of a paw.

Investigators believe the 5-year-old male African lion used a paw to lift a partially open door that was meant to keep him in a cage and out of the enclosure while Hanson cleaned, Hadden said.

“The lion had been fed, the young woman was cleaning the large enclosure, and the lion was in the small cage. The gate of the cage was partially open, which allowed the lion called Cous Cous to lift it up with his paw,” Hadden said. “He ran at the young lady.”

Hadden said Hanson was talking with a co-worker on a cellphone in the moments before she was killed. The co-worker became concerned when the conversation ended abruptly and Hanson failed to call back, the coroner said. The co-worker then called authorities when she went to check on Hanson. Sheriff’s deputies shot Cous Cous after he couldn’t be coaxed away from Hanson’s body.

Hadden said the investigation into Hanson’s death continues.

Hanson had been working for two months as an intern at Cat Haven, a 100-acre private zoo east of Fresno. Her father, Paul Hanson, described his daughter as a “fearless” lover of big cats and said her goal was to work with the animals at an accredited zoo. She died doing what she loves, he said.

That love was apparent on her Facebook page, which is plastered with photos of her petting tigers and other big cats. She told her father she was frustrated that Cat Haven did not allow direct contact with animals.

“She was disappointed because she said they wouldn’t let her into the cages with the lion and tiger there,” said Paul Hanson, a Seattle-area attorney.

The owner of the zoo said Thursday that safety protocols were in place but he would not discuss them because they are a part of the law enforcement investigation. Dale Anderson said he’s the only person allowed in the enclosure when lions are present.

“We want to assure the community that we have followed all safety protocols,” Anderson said. “We have been incident-free since 1998 when we opened.”

Friends of Dianna Hanson recalled her passion for cat conservation.

“She was lovely, energetic, athletic. She did everything she could to help our conservation efforts,” said Kat Combes of the Soysambu Conservancy in Kenya, where Hanson recently had volunteered to work in the Cheetah Research Center.

The reddish-haired young woman sustained numerous bites and scratches in Wednesday’s attack, and the autopsy revealed they were inflicted after she died.

“Which means the young lady … wasn’t alive when the lion was tossing the body about,” said Hadden, the coroner. “We think the lion hit her with his paw and that’s what fractured her neck.”

When the attack occurred, Anderson said he and two other Cat Haven workers had left to take a cheetah to exhibit at a school. Hanson and another worker were left behind.

Whether Hanson was performing a function that placed her in danger is being investigated by Cal-OSHA, which also is trying to determine if employees were properly instructed about potential danger, as required.

“There should have been procedures that very clearly stated what the employees were required to do in order to not get killed,” said agency spokesman Peter Melton, who added that documentation about the warning had not yet been provided by Cat Haven.

In addition, the U.S. Department of Agriculture, which enforces the federal Animal Welfare Act, is also looking to understand why the lion turned on the intern.

“We’re looking at whether the animal was acting in a manner leading up to that situation that maybe the staff should have been aware of,” spokesman Dave Sacks said. “Was it being fed properly? Was it under undue stress?”

USDA inspectors conduct multiple unannounced inspections of Cat Haven every year and never had found a violation, Sacks said. Federal regulations pertain only to animal treatment and do not “cover every single instance of what a facility can and cannot do,” he said.

A necropsy on the lion is being performed at the California Animal Health and Food Safety Lab in Tulare.

Cat Haven breeds and keeps lions, tigers, jaguars, lynx and other exotic cats and takes them out for public appearances. A recent television report showed a reporter petting one of the animals.

It does not hold voluntary accreditation from the Association of Zoos & Aquariums, said Senior Vice President Steve Feldman, or by the Global Federation of Animal Sanctuaries. Both set standards for members.

“There are very clear standards for care,” said Adam Roberts of Born Free USA, part of the federation. “Standards should not allow close contact with humans.”

By all accounts, Hanson loved contact with cats. In one photo on her Facebook page, a leopard is lying next to her leg.

Late last year, she traveled to a preserve where she had volunteered in Bellingham, Wash., and posted a photo of herself standing in a tiger enclosure holding a stick as she was preparing to scratch the animal’s back.

“I was bending over to scratch her back with my hand,” she wrote under the photo. “You only touch them with your hands … one doesn’t poke a tiger with a stick.”

On the same post, she expressed excitement about going to Cat Haven to start an internship. “So be prepared for more kitty pictures with new cats!” she wrote.

Hanson’s family was taking some solace in that she died doing what she loved.

“She was living her dream and pursuing her life’s work to the fullest,” her brother, Paul R. Hanson, told the AP. “Upon completion of college she set off to pursue her life’s work of bringing awareness of the plight of these magnificent animals through education and outreach.”

In a letter posted to family and friends, the woman who had graduated in 2011 from Western Washington University with a bachelor’s degree in ecology, evolution and biology talked about falling in love with exotic cats. After meeting a Washington couple with four tigers, she was hooked.

“For the last two and a half years I have been learning how to care for these animals and come next February, my father has given me a plane ticket” to Kenya, she enthusiastically wrote, adding later: “As my mother can tell you, I have had the goals of working with big cats since she adopted a tiger in my name when I was 7. I’m getting there.”