An NYPD administrative aid was arrested Saturday after fighting with an elderly relative, then slamming a door on the foot of an arriving cop, police said.

Kadi Willoughby, 54, got into a fight with the 75-year-old man at their home in Bedford-Stuyvesant, Brooklyn, broke his phone to prevent him from calling 911 and then locked him outside, cops said.

Willoughby then shut a heavy metal door on one cop’s foot, causing bruises, authorities said.

Willoughby, who has worked for the NYPD since 2010, was arrested and charged with assault, obstruction, resisting arrest and criminal mischief, according to police reports.