This happened in the Great Smoky Mountains National Park on the border of North Carolina and Tennessee. Some guy approached some bear cubs that were crossing a road with their mother.
He either he didn’t know or didn’t care that mother bears are fiercely protective . . . and this one started charging him, but then stopped once he backed away. The move is called a “bluff charge” and if he hadn’t backed up, she probably would’ve attacked.
https://www.youtube.com/watch?v=8DbY0GKAf10&feature=youtu.be