A fun-filled visit to the zoo turned into a tragedy for a family in Xi'an, capital of Shaanxi province, as a tiger attacked a man and his 17-year-old son, killing the former on the spot, on Sunday.

According to the Xi'an Qinling Wild Zoo, the man was killed by a 3-year-old male tiger at about 1:20 pm, but his son was rescued by zoo workers who rushed to the scene after hearing an alarm.

"We do not know how they (the man and his son) entered the tiger zone by foot, as visitors are required to take safety vehicles when entering the zone," an unnamed worker told China Daily on Monday.

Liang Guangzhou, a conservator of the zoo, who is in charge of managing the tiger zone, has been placed under criminal detention for his alleged negligence in the case by Chang'an sub-branch of Xi'an public security bureau.

Dang Bintao, a local hospital doctor who went to the zoo after the tragedy, said he and his colleagues found the man was killed on spot and his son was slightly injured on one leg.

According to policemen who went to investigate, the survivor is surnamed Zhang, a resident of Heyang county, who came with his father to the zoo after recently appearing for the college entrance examination.

"The boy said he and his 45-year-old father followed a vehicle to the tiger zone and were attacked by the wild animals," a police officer said.

"We followed the vehicle to the tiger area, where the first gate opened automatically and the second gate did not close. We did not notice the regulation (saying visitors are not allowed in the tiger zone on foot) printed on the back of the tickets," local media quoted Zhang as saying.

However, Shen Guancheng, general engineer of the zoo, said the park is divided into walking and vehicle areas.

"Visitors who want to see wild beasts, such as tigers and lions, must take safety vehicles provided by the zoo. The regulation is printed on the back of the tickets," Shen said.

He said every visitor to the zoo should read the instructions on the ticket before starting their tour.

"Even our staff is banned from directly walking into the vehicles-only area," Shen added.

The zoo has some 50 tigers and five of them, all males, were sent into the tiger zone for visitors to see on Sunday.

Wang Haogong, a lawyer at the Shaanxi Haogong Lawyer Office, said that the fault lies with the deceased, but the zoo is to blame as well for its management and should bear civil liability.

Wen Hongpei, a 38-year-old local resident who took her son to the zoo on Monday morning, refused to take her son to see the tigers and lions after hearing the news at the gate.

"I don't think the zoo can protect us thoroughly. There might be some loopholes in their management," she said.