San Francisco authorities weren’t able to explain on Wednesday how the 350-pound Siberian tiger escaped from its San Francisco Zoo enclosure on Christmas day.

If it is proven that it has made it on its own than all knowledge about the animal will have to be reshaped.

Ron Tilson, one of the top authorities in tigers and director of conservation at the Minnesota Zoo, said: “They don't jump very high, and they don't jump very far. Think of a sumo wrestler — much too massive for leaping — and that's the tiger,” The Seattle Times reports.

San Francisco police closed the zoo and treat it as a crime scene. They’ve wanted to find out if the tiger managed to escape by itself from its pen surrounded by a high wall or was helped.

Officials of the zoo said that the doorway of its pen was locked. This raises two question: if it is true or if the precautions in the zoo are not so good and could trigger a rethinking of the tiger pans.

Tatiana, the tiger, was shot by police on Christmas Day after she escaped from her pen with walls of 18 feet and a 20-foot moat. She killed a 17-year-old boy and injured severely two others that were standing in front of the zoo café.

According to Police Chief Heather Fong, a criminal investigation was opened to "determine if there was human involvement in the tiger getting out, or if the tiger was able to get out on its

The 17-year old victim was identified by the San Francisco Medical Examiner's Office as Carlos Sousa Jr.

Somewhere after 5 p.m. the tiger escaped and attacked Carlos, killing him on the spot. Afterwards she attacked two men of 19- and 23-year-old brothers from San Jose.

San Francisco General Hospital's Dr. Rochelle Dicker said that the two brothers underwent surgery and on Wednesday were stable. She said that they will recover and won’t have lasting physical effects, San Jose Mercury News informs.

Last year, Tatiana attacked a zookeeper when she was feeding her through the bars. After the incident the zoo installed better equipment.

It’s still unclear how the tiger escaped from its pen. The animal was hunted down by four officers after they’ve received a 911 call from a zoo employee.