Salem

Look at picture. Why I was KOed? Is this bug or I need to know something?

Bear has a fear that drains black bile on a long range. It's regardless of whether you're behind walls, across a river or anything of the sort. When he first "sees" you, he will hit you with fear until you either KO, go into a house/mine or move far enough to be outside his range.

Better luck next time LOL

Thank you

Well, as saw in your SS i get KO from his fear since your BB was really empty(the white fade square is only what would be recovering if you wasn't in a fight).
And bear fear can affect far away from him, the best is never near a bear if you can see it and run away if you can't fight with him.