SPOKANE - There will be no punishment for two adult grizzly bears that fatally mauled a 2-year-old grizzly at the Washington State University Bear Center, the director said Wednesday.

Charles Robbins said the Tuesday afternoon fight was the first time bears at the center had engaged in violent aggression. But the adults will not be moved or killed, he said.

"Nothing will happen to the older bears," Robbins said from the Pullman campus where the bear center is located. "It was not directed at us. They were simply being bears."

The three bears had been raised from birth in side-by-side pens and were together in a 2-acre outdoor fenced area when the attack occurred at about 3:30 p.m., Robbins said. Scientists have no idea why the older bears attacked, he said.

"Only the bears know what provoked it," Robbins, who founded the center in 1986, said. The bears had appeared to be friendly and playful with each other the past two weeks, he said.

In the wild, older adults will suddenly attack younger adult bears, WSU said in a statement on the incident.

"We have raised these bears from birth, and this is the first time they have exhibited any kind of aggression," said Lynne Nelson, the WSU veterinarian who oversees their medical care. "But they are still grizzly bears."

The bear center is a modest building on the edge of campus. It includes a series of cinderblock dens where up to 10 bears live. The bears are free to move outside, where they are separated from humans by two layers of chain link fence and can be viewed by anyone who stops in the parking lot. The policy is to let the bears out as much as possible so they can develop normal foraging and social interactions.

They are involved in a wide variety of research projects.

"All of us feel like we were kicked in the gut, so it will take awhile to get over," Robbins said.