The manager had a definite grievance, how would you like to work for years in a company and being promised by the father that he would one day be CEO and then being promised by the daughter and then the brother comes a long and now he's the acting CEO, yeah I would be annoyed, but I would hand my notice in and certainly not tried to kill someone, that's insane.
Oh no, you messed things up for yourself while you're still the manager. All you had to do was just let everything fall into place. Your day would come for you to be CEO because she said her elder brother would be the CEO in the meantime, not permanently. She would not let all the years you have been there and the hard work you do go unnoticed. You have cheated yourself out of being rewarded in its own timing since you poisoned the water to end the life of her elder brother from being the present CEO.
Never ever try to poison the CEO to get her/his position in the company because in the long run Karma will always come around on you and bite you in the butt or slap you in the face because you'll end up getting fired or going to jail
