Deputies responding to reports of an injured person at Cat Haven in Dunlap, California, found a severely wounded person inside the lion enclosure, Fresno County Sheriff's spokesman Lieutenant Robert Miller said.
"We don't know what happened leading up to the attack because there were no witnesses," Miller said.
Following the attack, another employee tried to distract the adult male lion away from the victim and into another enclosure but those attempts failed, the sheriff's department said in a written statement.
"Deputies shot and killed the lion to provide medical attention to the victim. The victim died at the scene," the sheriff's department said.
Authorities did not immediately identify the victim.
Representatives for Cat Haven, a 100-acre sanctuary that is run by the group Project Survival in Dunlap, about 40 miles east of Fresno, could not immediately be reached for comment by Reuters. The facility, which is located just outside of King's Canyon National Park, was closed on Wednesday.
The Fresno Bee, citing a spokeswoman for the facility, reported that the victim was a 26-year-old woman who had been working there as a volunteer intern and who had entered the lion's enclosure before the attack.
"Our thoughts and prayers are with her and her family at this critical time," Cat Haven founder Dale Anderson told the newspaper.
Several condolence messages were left on Project Survival's Facebook page. One person expressed sympathy for the loss of the employee and for a lion named "Cous Cous."
A 4-year-old male lion identified as "Cous Cous" is pictured on Cat Haven's website.
Janice Mackey, a spokeswoman for the California Department of Fish and Wildlife, said a necropsy would be performed on the lion to determine if it suffered from any health problems that could have led to the attack.
Anderson founded Cat Haven in 1993 "to exhibit a variety of wild cats and engage public support for their conservation in the wild via specific projects," according to the park's website.
