A man was shot to death last night in the Riverdale Park section of Prince George's County in an attack that raised the number of homicides in the county this year to a record.

The slaying in the 6300 block of 64th Avenue was the 155th homicide in the suburban Maryland county this year. The previous record of 154 homicides was set in 1991.

The name of the man who was killed about 7:45 p.m. on the rain-splashed street was not immediately available.

But the few facts available last night conformed to what police have described as the characteristics most typical of a homicide in Prince George's this year.

The slaying was committed with a gun, as were more than four out of five homicides this year. It occurred outdoors, on a street or other open area. The victim, who was black and in his twenties, was standing near some houses, police said. And he was shot on a Monday night inside the Capital Beltway.

As of late last night, there was no information about suspects or a motive.

A man at the scene who talked briefly to a Washington television station said he saw at least two people flee after the shooting.

The man told WTTG-TV (Channel 5) that he "saw them jump [a] fence" to get away.

He said he saw that one of them was wearing a mask when the person was partly over the fence and turned back to help someone else.

Other people interviewed in the neighborhood, which includes a low-rise, red-brick apartment complex, said they had not seen or heard anything about the shooting.

The previous reported homicide in the county occurred Nov. 17 in Oxon Hill. In that shooting, a 26-year-old man was found shot at his home on Alice Avenue.