15-20 years ago, such incident was so common. I've had it and moved to the US not because I couldn't endure such 'boss'-harassment, but because I found myself slowly becoming one of them. Being shout and poured water was nothing. Insulting, hitting, chuckling, throwing, etc was a daily life.
However, somehow productivity was sky high when a boss acts that way. And although boss looked crazy, we all had some respect that he/she is an abnormal or exceptional person and listening to the boss helps all of us. It still happens in Korea albeit in a much less frequency than 15-20 years ago. It's just that the sister wasn't respected by employees or went too far.
In sum, like some others, I believe this is a spin or distraction to other news stories in Korea. Yes, I heard the tape but it's not worth to be the top story.