Lion attack death: Entering enclosure a violation of zoo's rules, source says

(CBS News) The father of a woman mauled to death by a lion says he feared getting a call like the one he received on Wednesday. His daughter, a volunteer at a wild animal park in California, went into a lion's den by herself.

The massive 4-year-old lion attacked the woman inside an enclosure at this private zoo, east of Fresno. A source familiar with Cat Haven tells CBS News that accessing the lion's enclosure would mean violating the rules, by opening one of several locked doors.

Lion fatally mauls woman at Calif. sanctuary

Officials say a worker tried to lure the animal into a nearby enclosure so rescuers could get to the badly-injured woman. But when it didn't work, officers shot and killed the animal.

But it was too late for the dying woman, Dianna Hanson.

Dale Anderson, founder and executive director of Project Survival Cat Haven, said at a press conference, "Our thoughts and prayers go out to our friend and family and to her family at this time and through this trying time. We will keep you guys posted as things progress around here. Thank you."

"Couscous" the lion appeared on "Ellen" when he was just a few months old. The expert featured on the TV show said at the time, "Look at those claws. You can imagine what this guy is going to be like when he weighs five or six hundred pounds. Just incredible predators."

Investigators still don't know what provoked Couscous Wednesday.

Jack Hanna, director emeritus at the Columbus Zoo, said it's unusual for someone to go into an enclosure alone with a full-grown lion.

"It just doesn't sound right to me that no one was there with her in the cage with the lion," he said. "I don't know if it was feeding time or what went on, but that's the big question that has to be answered for me to understand what might have happened."

Hanna added, "Ninety-nine percent of the time, it's human error, when one of us gets hurt or injured or lose our life, so-to-speak, it's our fault, not the animal's fault."

And once someone enters the lion's den, Hanna said, all bets are off. "An animal like a full-grown lion in a situation can be like a grenade going off," he said. "It happens so fast. It's like nothing you've ever seen."

For Bill Whitaker's full "CBS This Morning" report, watch the video above.