I have to guess you were using a standard lens (50mm or so) so you were pretty close in that event. It wouldn't take many seconds for a grizzly to cover that distance.
Maybe you should get a 300 or 1000mm lens for better safety next time?
fortunately, this was taken from the safety of my car with a 300mm zoom, so i felt pretty safe at the time! thanks for the safety recommendations, however.