One person has been killed and two others injured after a tiger escaped from its cage at San Francisco Zoo.All of the victims were visitors to the zoo, a spokesman for San Francisco emergency services said.The Siberian tiger, named Tatiana, was the same one that mauled a keeper just before Christmas last year. It has now been shot dead.The incident occurred as the zoo was closing around 1700 (0100 GMT). It is not clear how the cat escaped its pen.[source]