Period or Comma?

I'm facing a sort of turmoil at present because of a co-teacher who made unreal issues about me. I used to look up to this person as a mentor, as an elder brother and most of all as a friend.
I hardly could not believe that the ones he uttered against "somebody" was passed to me. How dare him!
As a realization on my part, I should put a period on our friendship. Yes, Christmas is fast approaching and perhaps wounds have to be healed, disagreements have to be settled. I could be civil with him but I am not anymore his friend.
Some people are just born to act like snakes. He is one. Degrees are not really a guarantee that one acts accordingly. Attitude still comes out. I know, the truth will prevail but the damage has been done... I could not use a comma anymore. It's a period really...