A D.C. policeman was shot to death with his own gun yesterday afternoon during a struggle with a man he had stopped to question about a stolen car, police said.

Officer Donald G. Luning, 31, of 1054 Dorset Ave., Waldorf, Md., died at the Washington Hospital Center of a single gunshot wound in the chest about an hour-and-a-half after the 4:20 p.m. shooting, hospital officials said.

Luning, an 11-year veteran of the force, was assigned to the 6th District as a tactical officer and was in plainclothes at the time of the incident. He was married and the father of two young children.

Police arrested a suspect after a door-to-door search of an apartment building at 3694 Hayes St. NE. The suspect, Mark Anthony Watson, 19, of 1238 G St. NE, was charged with homicide, police Lt. Carl Alexander said.

Police cornered the suspect in a second-floor apartment of the Hayes Street building and began talking with him by phone about 6:40 p.m., according to Assistant Chief Marty Tapscott. "We talked to him in spurts," Tapscott said. "He made no demands."

Shortly before Watson gave himself up to police, he tossed a gun out the window of the apartment, Tapscott said. He said Watson surrendered after his father, Ellis Watson, arrived to talk with him.

About 150 officers participated in a door-to-door search of approximately a two-block-square area. The officers were assisted by helicopters and police search dogs. Powerful lights aboard fire department trucks flooded the area with light as the afternoon turned into early evening.

About 200 persons gathered at the scene as police negotiated with Watson. Two women, one identifying herself as Watson's aunt and the other as his cousin, pleaded with police not to harm Watson. They were taken close to the building where he had barricaded himself but were not allowed to speak with him.

When Watson, wearing cut-off blue jeans, white socks and light blue tennis shoes, was taken from the scene by police just after 8:30 p.m., the crowd of bystanders cheered the officers.

The incident began when Luning and his partner, Officer Nora Coaxum, 33, spotted a white Volvo, which they believed was stolen, in the 3700 block of Jay Street NE, police said. After confirming with the police dispatcher that the car had been reported stolen in Maryland, Luning and Coaxum stopped the car. When the two officers approached the car, the male driver and a female passenger ran, according to police.

Coaxum was able to overtake the woman and arrested her, police said. Luning chased the man into an apartment on the third floor of a building at 3712-A Hayes St. NE. Inside the apartment the man, who was described as about 6-foot-4, and Luning struggled, the man took Luning's service revolver and shot the officer with it, according to police.

Police said Elaine Wortham, 21, of 3749 Jay St. NE, was charged with unauthorized use of a vehicle. She and Watson will be arraigned today.

Luning is the first D.C. policeman to die in the line of duty in more than two years. Officer Arthur P. Snyder was shot and killed on Feb. 11, 1980, when he attempted to make a drug arrest on 14th Street NW.

Luning is survived by his wife, Jodie S., a daughter, Jennifer, 2 1/2, and a son, Matthew, 1 1/2.