Cat Haven founder and executive director Dale Anderson was crying as he read a one-sentence statement about the fatal mauling at the exotic animal zoo he has operated since 1993.
The intern was attacked and killed when she entered the lion's enclosure, he said.
He refused to take questions from reporters, but extended thoughts and prayers to the victim's friends and relatives.
The male African lion, a 4-year-old male named Couscous, had been raised at Cat Haven since it was a cub, said Tanya Osegueda, a spokeswoman for Project Survival, the nonprofit that operates Cat Haven.
Investigators were trying to determine why the intern was inside the enclosure and what might have provoked the attack, Fresno County sheriff's Sgt. Greg Collins said.
The facility, which is licensed by the California Department of Fish and Wildlife, is about 45 miles east of Fresno in the Sierra Nevada foothills. It is normally closed on Wednesdays, and only one other worker was there when the mauling happened, Collins said.
He said the county received an emergency call from Cat Haven about 12:30 p.m., and a second call 20 minutes later reporting the injured person had died.
A sheriff's deputy shot and killed the lion after the attack, California Fish and Wildlife spokesman Lt. Tony Spada said.
Osegueda did not know how the park acquired the cub.
Cat Haven is a 100-acre wild animal park just west of Kings Canyon National Park. Since the property opened in 1993, it has housed numerous big cats, including tigers, leopards and other exotic species.
Couscous was one of about two dozen animals at Cat Haven, which has had a good safety record, Spada said.
Another big cat sanctuary, Big Cat Rescue in Tampa, Fla., told the AP last year that at least 21 people, including five children, have been killed and 246 mauled by exotic cats since 1990. Over that period, 254 cats escaped and 143 were killed.
Tatiana, a tiger at the San Francisco Zoo, was killed by police after jumping out of its enclosure and fatally mauling 17-year-old Carlos Sousa Jr. and injuring two other people in 2007.
Cat Haven has housed Bengal tigers, Siberian lynx, caracals, jaguars and leopards of various types as well as bobcats native to the area. Its founder Dale Anderson, described the private zoo several years ago as one of a handful of facilities across the U.S. that has all of the big cat species in one place.
The facility's website says it promotes conservation and preservation of wild cats in their native habitats and offers visitors tours and educational outreach.