"Random variation" may be what's going on, at least if your reference is to the article reporting seven bear incidents. On the other hand, a mad scientist in Scotland (AFLM's evil cousin) may splicing genes from killer cobras into the black bear genome, and teleporting them to North American wilderness areas - this being first steps in his plan for world domination - simply unbearable!(Where's James Bond when you need him?)

The correct explanation probably lies somewhere between these two extremes.