(CNN) -- It was clear that Dianna Hanson was thrilled to be at the Cat Haven sanctuary. Her Facebook page boasted more pictures of lions and tigers than it did of her friends.
Hanson had been at the 100-acre wooded Northern California facility since January -- working as an intern, bonding with the big cats it's home to.
On a Facebook photo of her petting a tiger cub, a friend commented, "You have met your calling."
"My calling," Hanson jokingly responded, "drools on my pants."
On Wednesday, the 24-year-old Seattle woman was killed when she was mauled by a 5-year-old, 350-pound African lion inside a cage.
Hanson's grieving father said the lion, Cous Cous, was one of her favorites.
The sanctuary did not release details of why Hanson was in the lion's cage, but said it would investigate whether safety protocols were followed.
The Fresno County Sheriff's Office said that when the lion attacked, another employee at the sanctuary tried to distract him away from Hanson into another enclosure. "But all attempts failed," it said.
A sheriff's deputy shot and killed the lion to reach Hanson and give her medical assistance. It was too late.
"The victim died at the scene."
Facility 'well run, professional'
Hanson's father said he and his daughter took a two-day road trip from Seattle to Dunlap, California, at the beginning of the year when Hanson's internship began. She was supposed to be there for six months.
"Once there, she gave me the tour and showed me all the big cats there with which she would be working," the father, Paul, said in a statement Wednesday night.
"Of course, Dianna being Dianna, her favorites were the tiger and the lion ... who killed her today," he added.
Cous Cous once appeared on Ellen DeGeneres' television show when he was about three months old. The comedian fed him from a bottle as a handler stood by.
Late Wednesday, some who knew the lion, who had been raised in captivity, were shocked.
Jenny Michaels, the head of The Jungle Jenny Foundation, said she had been in the lion's cage before, accompanied by a park worker .
"I didn't see any type of aggressive behavior," Michaels told CNN's Piers Morgan.
She said the workers at the park were top-notch.
"It was really well run, very professional," she said. "I don't know the circumstances (of the attack) but I can tell you that in my interaction over at Project Survival they have been professional and ... they have run their protocol strictly."
Noted animal expert Jack Hanna said that even if Hanson knew the lion, a big cat can be unpredictable in the way it reacts to what it sees or hears.
"They are wild animals, end of story," he said. "No matter what anyone says, they are wild animals."
Hanna said it would be unusual for someone to enter an adult lion's cage without another person accompanying them or close by.
Big cat attacks
Twenty people, including five children, have been killed by big cats in the United States in the past 21 years, according to figures kept by Big Cat Rescue, a nonprofit cat sanctuary in Tampa, Florida.
Another 246 people were mauled in the United States during that same time period, 1990 to 2011, the group said. The group's website did not have figures for 2012.
In California alone, 14 people were mauled, but Hanson's is just the second death.
In 2007, an escaped Siberian tiger attacked and killed one person and injured two others in a cafe at the San Francisco Zoo.
Love of lions started early
Hanson's love for big cats began when she was very young.
"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 seven," Hanson wrote in a 2011 letter.
While working at a Washington ski resort while in college, she met a little boy who told her his grandparents owned four tigers. She befriended the family.
When she graduated from Western Washington University, her father presented her with a plane ticket to fly to Nukuru, Kenya, with the family and see the work being done with the animals there.
"I will be volunteering at the Cheetah research center, which is run by Project Survival," Hanson wrote in a college graduation letter. "They (also) have a facility in California known as Cathaven. The owners of Cathaven have invited me to see this facility, so I'm hoping to get down there this summer."
In the letter, Hanson thanked her family and friends for helping her get close to her dreams.
"This was her dream come true," her father told CNN affiliate KCPQ. "Working with big cats all day long, nothing but big cats."