A four-year-old female dolphin died Monday after suffering a fractured skull.
Nea died just before her scheduled 1 p.m. appearance at a Brookfield Zoo show, said zoo spokeswoman Sandra Katzen. .
Zoo authorities said the death was accidental, the result of a collision with another dolphin in the tank.
"Marine mammal staff responded immediately upon hearing a loud pop. When they noticed that she appeared injured, trainers jumped into the water and made heroic attempts to save Nea by performing CPR. Veterinary staff arrived in less than 10 minutes to assist, but Nea remained unresponsive," the release stated.
After the death, zoo officials canceled the remaining shows for the day.
Nea arrived at the zoo just last year. The average lifespan for a dolphin is between 17-25 years.