Why my father?

The chain of events I am responding to: returning home after summer away to find my father dead, my mother remarried, her new husband taking over my father's business, and then having reason to believe my stepfather murdered my father. First of all, I would be incredibly pissed off if no one had filled me in during the summer. To not be told, especially if they thought "it was for the best" and thought they were protecting me. Then coming home to some stranger living in my house and married to my mother who is supposed to be grieving after losing her husband would further my anger. This would also spark confusion on why had my mother so readily let go of her new life and began one without even mentioning a single aspect of it to me until she had no choice (when I returned home after summer). Maybe this man isn't so bad after all, I would try and give him a chance. Get to know him, especially because I would be living with him until I graduated, an entire year. But as soon as he thought he had a right to assume my father's job and business affairs, he would have crossed the line. He is not entitled to the success my father created from scratch just because he married my mother. If he was a "crazed lowlife" I would be afraid of him ruining my father's company and running it into the ground because of his lack of experience. As soon as I had reason to believe he took my father's life, he would be in for it. I would gather evidence but in private and secretly. If any adult found out, they would most likely contact my mother and make me attend counseling. They would say I was just grieving in my own way and was paranoid about my stepfather. It would all make sense to me. The murder to get my father out of the way, marrying his love (my mother), taking over his hardest work (his company), and finally he would silence me. He would soon realize that I knew everything. This would drive him to pay one of my close friends to spy on me. The final step before getting me out of the way. The only part I would not understand until there were more specifics would be why? Why my father and my family? Is he being paid by someone else? The past? Did something happen before I can remember? What is propelling him?