Sounds like a bit of a narcissist to me. Very charismatic, drawing attention to himself, false relationships, appearing to people to be oe thing while behind the doors is really another.

I doing think narcissists are even making a choice to behave that way. I believe it is a compulsion.

From experience I kknow it is difficult to watch and especially hard if you've no way of removing yourself from the situation. ARe you able to do so? Are you able to avoid him?

Are you in a position to warn people? In my experience I couldn't. I had to live with and bear it.