animal rights folks don't usually kill the thing they wish to see free, so I don't think that's it, besides, to efficiently kill that many reptiles that quickly without leaving any traces would be very difficult. I would suspect an airborn toxin, like maybe a new cleaning agent with something really toxic to reptiles in it was used by the janitor on the floors overnight, something fairly volatile and readily available at stores. is there a cleaning agent that toxic to reptiles that is used to clean floors? maybe a pesticide was sprayed to control flees in mamal exhibits but was accidently applied to the reptile area? anyway, super sad and rather devastating to conservation efforts, hope they figure it out quick and share with us what they find so we can all learn from the tragedy and apply the knowledge to best practices!