The incident occurred overnight when police officers were responding to a report of a man with a gun.
"Upon arrival, officers encountered individuals in and around a vehicle. Upon seeing the officers, two of the suspects fled on foot. During the foot pursuit, one of the suspects brandished a firearm. In response, an officer discharged their firearm one time, striking the suspect," the police said.
The suspect was taken to a nearby hospital.
"After all life-saving efforts failed, the suspect was pronounced dead. The other suspect made good their escape and was not apprehended. The decedent has been identified as 18 year-old Deon Kay, of Southeast, DC," the police added.
The incident comes in the light of nationwide protests against racism and police brutality in the United States provoked by the May 25 killing of an unarmed African American man, George Floyd, in police custody in the city of Minneapolis.