Sarah McClay, a zookeeper at the South Lakes Wild Animal Park in Cumbria, England, died on Saturday after she was mauled by a Sumatran tiger (video below).
McClay, 24, was in the tiger enclosure alone when she was attacked.
Police are investigating if the safety measures at the zoo failed, but the zoo's owner David Gill said McClay broke safety rules by going into the tiger enclosure while the animals were loose.
"Within two minutes we had firearms on scene, but sadly we just could not get a clean shot to do anything about it because of exactly where the animal was, so we did our best, we moved around to find a shot," Gill told Sky News.
"Very, very quickly I let off two shots to frighten the animals and it did what it needed to do, which was to lift them off and they ran back into the house and other keepers locked them up. Once we knew we were secure and safe, we went into the enclosure to retrieve Sarah."
McClay suffered traumatic injuries to her head and neck and went into cardiac arrest. She was resuscitated by paramedics and airlifted to Royal Preston Hospital, but died.
Gill told the BBC: "After investigation by the authorities here and the police, it does seem that she just basically failed to follow the correct procedures. For some unknown reason, an inexplicable reason, because there is no reason for why she did it, she opened the door and went into the tiger enclosure and straight into the tigers, and now we'll never know why."
"...All we know is that no one else was involved, there was nobody with her, and for some unknown reason she opened a door and walked straight into the tigers."
Gill called McClay "a very passionate girl, very enthusiastic" who was "extremely good at delivering conservation talks. A very valued part of our team. A very bubbly character, a very happy girl."
There are no plans to put down the Sumatran tiger, which is what often happens in the U.S.