who did it in the residence

The person who did it in the residence, specifically the murder of A.B. Wynter in the White House as depicted in the series "The Residence," is Lilly Schumacher, the White House social secretary. She killed A.B. because she hated the institution of the White House and what it represented, especially A.B. Wynter who embodied the traditions she wanted to change. Lilly orchestrated the murder by sealing a door to conceal the crime scene and tried to shift blame onto others, but Detective Cordelia Cupp ultimately uncovered her guilt