When I was a kid on a family trip to Gatlinburg, we came across a momma bear and three adorable, little cubs. Two of them started wrestling and my dad, being a bit of a photo hound, started furiously taking pictures. He got some great ones. However, with his attention focused on the two wrestling cubs, he failed to notice that the third cub had wandered around behind him and he was sitting right between him and his momma. She reared up, growled, and feigned a charge. Luckily, it was just a threat. She allowed my dad to slowly back away from them, where she could see the cub again, and she settled back down.
We got pretty lucky that we weren't rushing my dad to the hospital, or worse.