A freak dolphin collision at an Illinois aquarium killed a young female, reports ABC News. Trainers did not see what happened, but say the dolphins were playing when they heard a "pop" just before an afternoon show earlier this week. They rushed the 4-year-old bottlenose dolphin into a medical pool, but were unable to revive her. "It's a devastating loss for the staff and for our zoo and for anyone who had a relationship with her," said a trainer. (More dolphin stories.)