Santiago - A zoo in Chile's capital said it was forced to kill two lions on Saturday to protect a suicidal man who had entered their cage in front of aghast visitors.Security protocols kicked in immediately when staff saw the man climb down with a rope into the African lions' enclosure, the head of Santiago Zoo, Alejandra Montalva, told television network TVN.The carnivorous felines, a male and a female, instinctively attacked and had to be put down. Anaesthetic darts would not have stopped the attack in time, she explained."We're shaken by this because the animals in the zoo are part of our family," Montalva said."These were lions that had been with us for more than 20 years."The man, in his 20s or 30s, was taken to a hospital with critical injuries.