San Francisco ? A tiger that mauled a zookeeper last year escaped from its pen at the San Francisco Zoo on Tuesday, killing one man and injuring two others before police shot it dead, authorities said.

The three men were in their 20s; they were together and were not zoo employees, San Francisco Police spokesman Steve Mannina said.

They were attacked just after the 5 p.m. closing time outside the zoo’s Terrace Cafe on the east end of the 1,000-acre grounds.

It was unclear how the tiger escaped or how long it was on the loose. The Siberian tiger, named Tatiana, attacked a zookeeper last December during a public feeding, according to the zoo’s director of animal care and conservation.

Police arrived to find the tiger on top of a victim.

The tiger then started moving toward a group of approaching police officers, and they opened fire with handguns, Mannina said.