UPDATED 09/06/11 1:13 p.m.

BROOKFIELD, Ill. (CBS) — A 4-year-old Atlantic bottlenose dolphin died Monday at the Brookfield Zoo.

READ MORE: Woman Critical, 1 of 6 People Wounded In Lawndale Mass Shooting

As WBBM Newsradio’s David Roe reports, the dolphin, named Nea, died just before a show was to be put on at the zoo after an apparent accidental collision with another dolphin.

LISTEN: WBBM Newsradio’s David Roe reports

Staff who care for the marine mammals say they responded immediately after hearing a loud pop.

Trainers said they jumped into the water and tried to save Nea by performing cardiopulmonary resuscitation.

Veterinarians were on the scene in less than 10 minutes. But Nea didn’t make it.

READ MORE: Young Woman, 18, Dies After Being Shot In West Elsdon

Preliminary results of an animal autopsy performed later Monday indicated a fractured skull. Zoo experts believe that Nea received her fatal injuries from colliding with another dolphin rather than a hard fixed object, which would have caused scrapes or bruises.

“We checked for all those signs, and there was absolutely nothing else there,” said Bill Zeigler, senior vice president of animal care and collections. “So whatever she hit, it was a soft object. It wasn’t the side of a pool which would be hard. That kind of abrasion would have shown up.”

Five of the seven dolphins are younger, Zeigler said. “They’re like a bunch of kids running around. We just think they happened to collide.”

Nea’s death “devastated” the workers who cared for her, said Rita Stacey, curator of marine mammals.

“She was a wonderful animal to work with. Anybody who had worked with her just instantly fell in love with her. She was a very fun-loving, very cooperative animal. She always wanted to work with and play with the trainers,” Stacey said.

Dolphin shows at the zoo were canceled for the rest of the day Monday, but will resume as usual on Tuesday.

MORE NEWS: Chicago Fire Paramedic's Cap Grazed At Stroger Hospital; Man Killed In Shooting Nearby

The Sun-Times Media Wire contributed to this report.