Crime investigators have moved in to the zoo in America where a visitor was killed by a tiger on Christmas Day.
Police are investigating the possibility that the three men involved in the attacked may have provoked the animal, or even helped it escape.
The two other men were seriously hurt and are being treated in hospital.
The animal - a Siberian tiger called Tatiana - was killed by armed police who were called to the incident at San Francisco zoo.
Zoo keepers say they don't know how the creature got out of her enclosure, which is surrounded by a high wall.
The dead man has been named as Carlos Sousa, 17, from San Jose.
The injured men - aged 19 and 23 - are expected to make a full recovery, doctors say.