"It may be an indication of what happened," Worstell said. "There's obvious signs of stress and malnourishment. Maybe (the sow) was desperate."
The year-old cubs each weighed only between 60 and 70 pounds, versus a normal range of 80 to 130 pounds. Wildlife officials are investigating what caused the cubs to be malnourished. Grizzlies are omnivores and eat everything from berries and ants to fish and elk.
Kevin Kammer, 48, of Grand Rapids, Mich., was killed and two people were seriously injured when the adult bear ripped into several tents Wednesday at the Soda Creek Campground near Cooke City, an old mining town just outside Yellowstone National Park.
The 300- to 400-pound sow was euthanized Friday after DNA tests linked it to the attacks. Wildlife officials have said she appeared to be healthy, but they intend to further study the body in hopes of explaining her behavior.
Worstell said the cubs will remain in quarantine for at least 30 days to make sure they are disease-free.
The zoo has one other grizzly, a year-old male obtained from Yellowstone National Park that had been seeking food from park visitors. The zoo also has a 10-year-old Eurasian brown bear.
The three cubs aren't expected to be available for public viewing until fall.
Wildlife officials say the cubs likely participated in the attack on Kammer, and so cannot be released back into the wild having probably learned from their mother's behavior.