The director of the San Francisco Zoo admitted Thursday that the wall surrounding the zoo's tiger enclosure is shorter than the height recommended by a zoo accrediting agency.

Zoo Director Manuel Mollinedo said the wall is 12.5 feet tall, while the Association of Zoos & Aquariums recommends a minimum height of 16.4 feet.

A tiger escaped at the zoo on Tuesday, killing one zoo visitor and mauling two others.

Mollinedo said safety inspectors examined the wall, and never raised any concerns about its size. He said now they'll be "revisiting the actual height."

As police continue to investigate the incident, Mollinedo promised that extra precautions are being taken to ensure visitors' safety.

At a Thursday afternoon news conference, Manuel Mollinedo said a new fence would be installed in front of the zoo's tiger exhibit along with surveillance cameras. Electric wire will also be added around the animals' habitats, he said.

"The zoo will be safe when it reopens," Mollinedo said.

Was Tiger Taunted?

Authorities are reportedly investigating whether any of the victims in Tuesday's fatal tiger attack taunted the animal before it went on a rampage.

The tiger mauled three zoo visitors, killing 17-year-old Carlos Sousa Jr. and critically injuring two young men before being shot to death by police. The two survivors have undergone surgery for deep bites and claw wounds to their heads, necks, arms and hands, and doctors expect both of them to recover fully.

The San Francisco Chronicle reported that police found a shoe and blood in an area between a gate and a moat in the tiger enclosure, raising the possibility that one of the victims dangled a leg or another body part over the moat.

Police Chief Heather Fong said investigators had found a shoe print on the railing in front of the tiger exhibit and were comparing it to shoes from the three victims. However, she said there was no truth to the other Chronicle reports.

Meanwhile, the father of the 17-year-old who died in the attack said he doesn't think his son would taunt animals.

Carlos Sousa told ABC's "Good Morning America" that he hopes it's not true. He added that no one deserves to be the victim of such an attack, "taunting or not taunting."

Sousa said "animals should be protected from the people and the people should be protected from the animals."

The San Francisco Zoo will remain closed Thursday as police continue what is now a criminal investigation into the Christmas Day tiger rampage.

"It was hard to look at a body bag and say, 'Oh, that's my son,'" Sousa Sr. told the San Francisco Chronicle. "Right now, I am going through shock. It's hard to believe. I want it to be a dream."

The attacks happened about an hour before the zoo's 6 p.m. closing time and it's not clear how long the tiger had been loose. One zoo official said it did not get out through an open door, and must have climbed or leaped out of the enclosure. But some wildlife experts say it would be "virtually impossible" for a captive tiger to have jumped from the exhibit.

Mollinedo said he examined the habitat area along with police following the incident and found no gates or doors unlocked.

"Every lock was in place," he said. "There was absolutely no way the tiger could have escaped from the back portion of the exhibit or the building."

Officials from other zoos around the country are being brought in to help re-evaluate the zoo's big-cat exhibit.

Police Call Zoo Crime Scene

Fong said they were not certain whether the incident involved any "human action."

Police said they're confident there were no other victims. They searched the zoo grounds during the night using searchlights and thermal imaging equipment, and again during daylight.

The same tiger ripped the flesh off a zookeeper's arm just before Christmas a year ago while the woman was feeding the animal through the bars. A state investigation faulted the zoo, which installed better equipment at the Lion House, where the big cats are kept. The San Francisco Chronicle said the zoo was slapped with an $18,000 penalty.

Mollinedo said Wednesday that he gave no thought to destroying Tatiana after the 2006 incident because "the tiger was acting as a normal tiger does." As for whether Tatiana showed any warning signs before Tuesday's attack, Mollinedo said: "She seemed to be very well-adjusted into that exhibit."