Liang expressed that he just wanted to do right for her mother, and I think paternalism is quite suitable to interpret his act. Paternalism, derived from the best interest, allows one to make decisions for another. In the bioethics literature, paternalism defined as "the interference with a person's liberty of action justified by reasons referring exclusively to the welfare, good, happieness, needs, interests or value of the person being coerced." (ref). Liang delectrocuted his mother with no collaboration with her on decision making, terminating her life. To Liang, the best interest is to solve his financial hardship as he is the breadwinner of his family. Liang could not afford the huge medical treatment fees and ending his mother life can lessen the burden. But what is the best interest for Liang's mother, together with her welfare, good, happiness, needs or value?.
Liang made his decisions because his mother was in a comatose state and his interference with his mother's autonomy is understandable, say for instance that he may be using his mother's money to pay her hospital fee. What I am most concerned is why he made such a crucial decision, ending her life on behalf of his mother?.
Liang's mother also has the right to live. The matter was, was she leading a good quality of life and does it worthy to continue her life under her condition before Liang ending her life? Liang saw his mother suffering so much, as she went into comatose after stroke with incontinent and unable to speak, eat or move. Surely, Liang's mother was lack of the basic fundamentals to lead a meaningful life, as she was unconscious. Before Liang decided to kill his mother, a doctor told him that there was no hope for improvement. Foreseeing that his mother may continue to live without conscious right to make any choice for herself, may further deteriorate and even worse was without enough money to provide the best quality of care, Liang made such a decision for his mother.