The incident took place on Wednesday night in the 1000 block of Poplar Grove Street.
The victim told authorities that the suspect, Jermaul Dean, frisked him and went through his pockets. He then ordered the victim to put his hands on his head and took $75 from him.
The victim provided police with a description of the suspect and his vehicle.
That description helped police find the car in the 2800 block of Riggs Avenue.
Investigators said Dean admitted to having a badge in the console of his vehicle.
The suspect told authorities he was preparing to enter the police academy.
Dean has been charged with assault, theft and robbery.