Three grizzly bear cubs whose mother killed one person and mauled two others in a late night attack at a Montana campground were malnourished and still in their winter coats.

The cubs have arrived at their new home at ZooMontana in Billings. Zoo executive director Jackie Worstell says Sunday the two female cubs and one male cub showed signs of stress that may help explain their mother's unusually aggressive behavior.

Forty-eight-year-old Kevin Kammer 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.

The 300 to 400 pound sow was euthanized Friday.

Worstell says the cubs will remain in quarantine for at least 30 days to ensure they are disease-free.