Typical with black bears scare them away, in this case it appears to be a problem bear that has been accustomed to humans due to people feeding it resulting in them not fearing people. For them likely walk away get help.
Scare it away or leave as it munches. It's a cub so I probably wouldn't try scaring it in case mommy is nearby but it's a black bear so you've got a good chance of keeping all your body parts.
I mean while I am not going to try and fight a bear, I would like to think that I would put down the phone and distract it while my family gets away from it.