(CNN) -- A Siberian Tiger mauled a man Monday morning after he and a friend scaled the fence of the Calgary Zoo and pressed up against the tiger cage, zoo officials said.The information we have is that while his injuries appear not to be life-threatening. They are, however, quite serious," Graham Netwon, the zoo's director and chief financial officer, said at a news conference Monday.
Officials said two men scaled the zoo's 8-foot perimeter fence, which also is covered in barbed wire, about 1 a.m. Monday morning.
The two 27-year-old men, who were not identified, then headed toward the tiger cage, where they scaled a safety fence meant to keep the public away.
The two men never entered the cage, but stood in between the safety fence and another fence meant to "keep the tigers in" when they startled a 2-year-old Siberan tiger named Vitali.
Vitali "has a fairly significant armament at his disposal: very sharp claws," said Dr. Sandie Black, the zoo's head veterinarian.
Once the tiger was startled, he probably clawed one of the men, officials said.
"My guess would be that the gentleman was hooked by a claw and the arm dragged in and then continued to be attacked from that point," Black said during the news conference.
The second man then struggled to help his friend escape the tiger's grasp, officials said.