You really didn't know what you were going into. The new zoo was a lot different to the other zoos that were around. People did come flocking to the zoo, but not many left the zoo. Some of them stayed. Some of them became a part of the zoo. These zoo animals were rather intelligent and with that came the power to change people. These zoo animals were intelligent enough that they could stop their own extinction by changing those around them to add to the herd. The people affected wouldn't even notice the change, they would just follow their new animal leaders. There were people still showing people around, but they weren't people. They've been animals before, they just want to add more to their pack, to their herd. This was a zoo where you could barely escape from being changed to be a part of them. At some point, you will become one of them. A zoo where the animals run the show...
...but you didn't know that and you still decided to go.