Recently a bear pulled a sleeping boy scout out of his tent...
http://www.freerepublic.com/focus/f-news/943370/posts
A woman from Ohio is hospitalized with serious injuries after a bear attacked her near her home in Ashtabula County ...
http://www.freerepublic.com/focus/f-chat/1636916/posts
Its amazing how many people are trying to rationalize this attack as due to some degree of carelessness on the part of the campers with no evidence to indicate it was the case.
Bears are opportunistic omnivores, e.g. they eat anything they can get ahold of and overpower - roots, berries, rodents, deer, even other young bears, etc. This bear just concluded that there was something edible and available there and took advantage of the opportunity for a meal.