woman who killed twin sister found not criminally responsibleTracy Chen killed sister because she believed she was possessed by entity that planned to kill herWARNING: This story contains graphic details.This week, Tracy was found not criminally responsible for Ivy's death and dismemberment — the final act in a family tragedy almost impossible to contemplate.A downstairs tenant told RCMP she heard frequent arguments in the unit above: "mostly one side, shouting ... kind of spouts of rage" and a "barrage of aggression.""The noise was described as the sound of a female 'wailing in this despair' in the bedroom directly above her," according to the admission of facts."She believed that this had to be done by her birthday, which was in May of 2020, and that led her to purchasing the tools that she ultimately used to dismember her sister with.""