the old woman was playing disabled and killed her care keeper

when you a fbi agent and u get a case that a woman was murdered . she had a job but was taking care of her great grandma and her great grandma was disabled and an a will chair. you found the body in the kitchen . you ask her some questions from the bottom of the stairs then she replies good and decently but then you tell her to move out of the way so you can use the phone upstairs she moves out the way you try to use the phone but then you realize how did she get up the stairs if she is in a will chair and her care keeper is dead down stairs in the kitchen