A dozen stingrays at Tampa’s Zoo died in their touch tank under mysterious circumstances this week, officials said. Workers noticed unusual behavior among the rays on Thursday morning, and within an hour, every single one was dead, the Tampa Bay Times reported. A preliminary investigation found no problems with the tank conditions, and now staffers are waiting on toxicology results. “It’s like a day out of your nightmare, pretty much,” ZooTampa’s Dr. Cynthia Stringfield told the newspaper. “We’re really focused on trying to get to the bottom of what happened.”