A Prince George's County teen-ager was fatally shot yesterday in a Southeast Washington apartment apparently after fighting with his teen-age brother and two men, D.C. police said.

James Singleton, 16, of 10218 Prince Place, Largo, was shot once in the chest after he argued with his brother and two men about 1:30 p.m. as he tried to rob a tenant at 1321 Anacostia Rd. SE, according to police. Singleton was taken to D.C. General Hospital and pronounced dead at 2:29 p.m., police said.

The brother, 19-year-old Gregory Gilchrist was arrested and charged with felony murder. Gilchrist, who lives at 1417 Billings Ave., Capitol Heights, did not shoot his brother but was an accomplice to the slaying, police said.

Singleton's death is the 52nd slaying to occur in the District this year, according to police statistics. Thirty persons had been slain in Washington at this time last year, police said.

Shortly before yesterday's shooting, Singleton, his brother and an unidentified friend had driven to the two-story Anacostia Road apartment building to rob an unidentified man who lived there, police said.

"Singleton definitely went over there as part of a team to rob or burglarize the place," a homicide detective said. "But we're still not sure how that unraveled, or exactly why he was shot."

Detectives said it was unclear if drugs were involved in the slaying.

Police said they were seeking the unidentified friend in connection with the incident, and added that Singleton may have been accidentally shot.

Cherie Hill, who said she was Singleton's 19-year-old cousin, said she was in the apartment building, which rests on a narrow, winding road one block above Minnesota Avenue SE, when the fighting and shooting began.

"I think Greg and James came with their friend to get money from my boyfriend," she said a few hours after the shooting. "They kicked the door down, and that's when I ran out. Then I heard two shots, and saw James run outside. He was staggering and bleeding, and he fell to the ground."

Hill said she called police and tried to resuscitate Singleton.

James Singleton was a "mannerly" and "helpful" teen-ager, according to his next door neighbors in Largo. Neighbors Larry and Perl Chase said they did not know Singleton well and thought he lived only part time with his mother, Georgia Singleton, in her three-bedroom condominium apartment at the Pines, near Prince George's Community College.

"He would ask if he could help carry groceries or offer to pay to use the phone," said Perl Chase. "He was always neatly dressed, usually wearing a jogging outfit."

Staff writer Linda Wheeler contributed to this report.