A 24-year-old man was mauled to death by at least one grizzly bear while cleaning out the captive-bred animal's enclosure.
The bears were kept by Animals of Montana, a casting service that provides exotic animals for photo-shoots and films.
Authorities were called to the centre on Sunday morning at 10:24 a.m. and the sheriff's office reported shortly after that a man, originally from Pennsylvania, had been killed while cleaning.
One bear had to be put down to retrieve the victim's body.
A spokesman for Animals of Montana said: "It's obviously a tragic situation, and I don't think we'll ever know exactly what happened."