A 22-year-old Silver Spring woman was charged Monday night with first-degree murder in the slaying of a teenager who police said was killed because "he knew too much about her drug-selling business."

Parris D. Pratt of the 100 block of Croydon Court shot 16-year-old Philip Cunningham in the head several times Thursday night on a quiet street in Silver Spring after taking him for a ride in her car, police said.

Police were initially unable to identify the victim, who lived at a group home in the District. On Sunday, they received a call from a male who said he was a friend of the victim's and had witnessed the shooting.

The informant, whom police did not identify, told detectives that he and Cunningham were walking down the street Thursday when Pratt pulled up and asked them to get in her car. Police said the suspect and the victim knew each other but declined to characterize the nature of their relationship.

"This was not a stranger picking up a stranger on the side of the street," said Montgomery County State's Attorney Douglas F. Gansler (D). "This was a preexisting relationship that stemmed back to their ties in the District of Columbia."

Pratt drove the two males to the 9200 block of Manchester Road, where she got out of the vehicle and told the two passengers she needed to use the restroom, according to police. The informant told police that Pratt returned to the car a few minutes later, after walking into bushes next to the road.

"When Parris came back to the car, she knocked on the window and asked to speak to Cunningham away from the car," according to a police statement. Cunningham exited the vehicle and walked toward Parris.

Police said the witness told them that "Parris then produced a silver revolver and shot Cunningham multiple times." Pratt got back in the car and was starting to drive away when she noticed Cunningham was still alive, police said.

"Parris exited the vehicle, walked back over to Cunningham and shot him again while he was lying on the ground," the witness told police.

Yesterday, detectives visited Pratt's employer, where they obtained a photograph of the suspect. Investigators showed the photo to the witness, who identified her as the killer.

Police took Pratt into custody yesterday. In an interview with detectives, she "admitted to being involved in the shooting of Cunningham," police said.