Allena Hansen's personal Bearpocalypse started with a wildfire in California, near the Sierra Nevada Mountains. The bears and other wildlife fled their natural habitat (because it was on fire) and spread out into places that humans tend to live. Allena went from having seen seven or eight bears in her entire life to seeing that many bears in her back yard.
Though, to be fair to the bears, the invasion went both ways. Ever since the recession hit, people have moved farther away from expensive cities and farther into areas where bears typically live. (It is much cheaper to rent an apartment in the Hundred Acre Wood than it is in Manhattan.)
The problem is that as soon as a bear gets a taste of anything human -- from drinking out of your garden hose to eating out of the garbage -- forest authorities have to take it out. Otherwise, it will never leave; getting food and water from people's houses, camps, toilets, etc. is way easier than wasting an entire morning trying to catch fish or desperately licking honey out of a pulsating beehive.