A 19-year-old Seat Pleasant man was shot to death during a running gun battle between two cars speeding down Silver Hill Road, and a 20-year-old Landover man was killed in an unrelated shooting outside a neighborhood crab house early yesterday morning, Prince George's County police said.

Antonio Keith Brown, of Hilton Street, was shot once in the chest about 1:35 a.m. during a gunfight between the occupants of a Nissan Stanza and the car in which he was riding, police said. Brown, who was driven to Greater Southeast Hospital by his friends, was pronounced dead about 30 minutes later, police said.

The shooting began, police said, after what the youths described as a random, obscenity-filled argument over nothing in particular. Such encounters in which youths perceive that they have been disrespected -- "dissed" in the parlance of the street -- have led to other fatal shootings over the last year in the District and Prince George's.

In this instance, the three youths riding in the Chrysler station wagon with Brown told investigators they traded insults with four youths in a tan or peach-colored Nissan when they stopped at a traffic light on Silver Hill Road. The youths, who told investigators that they did not know their assailants, said one of the passengers in the Nissan began shooting at the station wagon as they drove away, police said.

Brown then drew his handgun and returned the fire as the two cars raced down Silver Hill Road between Brooks Drive and Suitland Road, police said. The gunfight lasted for about two blocks as the cars sped along the road, on which patrons frequently travel to and from nearby clubs and bars in the early morning hours, police said. Investigators said they do not know whether anyone in the Nissan was injured.

About 20 minutes later, outside Jimmy's Crab House in the 7200 block of Landover Road in Landover, Rodney Theodore White was shot once in the chest. White, who lived nearby in the 2600 block of Pinebrook Avenue, was pronounced dead at Prince George's Hospital Center, police said. Police said people in the area reported hearing a single gunshot. A man wearing a dark hooded coat was seen running from the direction of the crab house about the time the shots were heard, police said.

No arrests were made in either case. The slayings brought the number of homicides reported in Prince George's County to 99 for the year, one fewer than the number reported at this time last year, police said.