1- Mrs. Stanning is killed first to get her out of the way because she is Trotters adopted mother, Mrs. Boyle was the reason he was sent to the abusive foster home.
2- Mollie used to be Trotters brothers teacher and Giles was her husband, the letter that trotter sent her was received to late do to illness, so he had a deep hatred forming for her.
3-Trotter goes with his sister to a "safe place" when she states he need mental attention
Hope this helps!
