SAN FRANCISCO, California (CNN) -- A wall that separated the public from the San Francisco Zoo's tigers is nearly 6 feet lower than initially reported -- and nearly 4 feet lower than industry standards -- the zoo's director said Thursday.

The killed teen's father, Carlos Sousa, told CNN on Thursday that the zoo should do more to protect visitors.

A 300-pound Siberian tiger apparently jumped that wall Tuesday, zoo director Manuel Mollinedo said, attacking and killing a 17-year-old boy and injuring two other young men, brothers who were visiting the zoo with the teenager.

"I think the tiger could have grabbed onto something, maybe a ledge," Mollinedo said. "She had to jump. How she was able to jump so high is amazing to me, but she's an exotic animal."

Mollinedo also said the dry moat between the wall and the tiger exhibit is 33 feet, not 20 feet as originally reported. The wall, he said, is 12 and a half feet, not 18 feet. The exhibit was built in 1940, he said.

Accreditation inspectors who visited three years ago "never noted that as a deficiency," Mollinedo said. "Obviously, now that something has happened, we're going to revisit that."

Meanwhile, police say they have no information suggesting the teenager who was mauled to death dangled his leg over a railing which surrounded the animal's exhibit. Watch dad call safety measures insufficient »

Investigators are analyzing a shoe print on the railing, San Francisco Police Chief Heather Fong said Thursday.

The investigation is looking into the possibility that the tiger escaped by latching on to a leg or other body part of one of the victims to get out of its enclosure, the San Francisco Chronicle reported.

"We are analyzing the shoe print and we have no information to tell us at this point that they did or did not go over the rail," said Fong.

The zoo will remain closed Friday. Mollinedo said the Lion House, which houses the zoo's big cats, will remain closed and the animals would be "kept in cages in back of the exhibits at the Lion House" for the time being.

"When we open the zoo, the zoo will be safe," he said.

The female tiger named Tatiana killed Carlos Sousa, 17, of San Jose, California, just outside the animal's den, said Fong. Watch more on clues from the deadly attack »

One of two brothers were also outside the den. One was attacked there while the other brother ran about 300 yards toward a cafe at the zoo, knowing that there were likely people there, Fong said. The incident began shortly after 5 p.m. and most of the zoo's patrons had left.

The tiger followed the brother running toward the cafe and attacked him there. Police arrived at the cafe and shouted at the animal to distract it. But Tatiana began attacking again, and authorities shot and killed it.

The brothers survived and are recovering at a San Francisco hospital. Doctors are focusing on ensuring that the patients don't develop infections. The pair will be on antibiotics for some time, a physician said.

Authorities carried out multiple searches to ensure there were no other victims in the zoo, Fong said.

On Thursday, Mollinedo ruled out the possibility that the tiger escaped through a building in the rear of its exhibit.

Along with detectives and zoo staff, he inspected the building in back of the exhibit and other rear exits the tiger might have taken to get out. The animal keeper was also questioned, Mollinedo said.

"Every lock was in place," he said. "There was no way that tiger could have escaped through the building. The tiger must have escaped through the front location of her exhibit."

Mollinedo was asked Wednesday about an incident last year, in which Tatiana chewed flesh off a keeper's arm during a public feeding demonstration. He said that Tatiana "was acting like a normal tiger" at the time, and that the zoo modified procedures to increase safety.

In that incident, California's Division of Occupational Safety and Health determined the zoo was at fault because of hazardous conditions in the Lion House and lack of specialized safety training for employees. The zoo made changes that the state safety division ordered. The Lion House was closed for more than six months after the incident.

Carlos Sousa's father, also named Carlos Sousa, criticized the zoo's safety Thursday.

"They didn't do enough for the public, because I think the zoo should be protective on both sides, protective for the people and protective for the animals," he said. Read about other escapes and attacks by captive animals

The teen's mother Marilza Sousa told CNN on Thursday that Christmas would never be the same for the family. "This is supposed to be the day for giving, not to take. And he was taken away from me," she said holding back tears. Watch legal analyst say a suit by victim's family is likely »

The head of the Association of Zoos and Aquariums said this was the first-ever visitor fatality due to an animal escape at a zoo accredited by the association.

Jim Maddy issued a statement expressing "sympathy to the family of the guest that lost his life, and our deepest hope that the two injured guests will recover."

Maddy called the San Francisco Zoo "great."

"Until this incident, there had not been a visitor fatality resulting from an animal escape at an AZA-accredited zoo.

"AZA mandatory accreditation standards require safety and emergency protocols that go beyond federal, state or local requirements. Regular safety training and annual emergency drills are required by these mandatory accreditation standards," he said.

He said association rules "require that the San Francisco Zoo provide a thorough report to its independent accreditation commission, which will review it and determine any actions that need to be taken. We will not speculate on what action might be taken until the facts are fully reviewed."

Sousa's sister Beatrice told CNN Wednesday night that the family has not received information about the investigation. "There's a lot of pain. You know, no words for it. It's just too much," she said. "Our family is very, very hurt."

Ron Magill of Florida's Miami Metro Zoo told CNN that the Siberian tiger is "the most powerful cat on the face of this planet."

Four-year-old Tatiana was born at the Denver Zoo and came to San Francisco in 2005.

Along with Siberian tigers, an endangered species, the zoo has rarer and smaller Sumatran tigers. E-mail to a friend

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