The slaying of two Northwest women Wednesday was described by police sources yesterday as the act of a man angry and vengeful over his romantic breakup with one of the women's relatives.

Police went to question a suspect at his apartment yesterday, but he escaped after confronting two D.C. detectives with a gun, police sources said. No shots were fired, police said.

The bodies of Mabel Gordon, 76, and her grandniece, Marcia Blackstock, 21, were discovered by firefighters who arrived to fight a small blaze Wednesday afternoon at the women's home at 1513 Buchanan St. NW.

Gordon, who was found on the dining room floor near the top of stairs to the basement, had been shot several times, sources said. Blackstock was discovered on a bed in the basement. She had been shot, stabbed and strangled with an electrical cord wound tightly around her neck, sources said.

Police believe that the killer may have set fire to the bed on which Blackstock's body was found in an effort to cover up the slayings.

The suspect apparently had dated a relative of the slain women who lived at the row house in the quiet, tree-lined neighborhood, but she wanted to break up with him, police sources said. In anger, he had recently beaten her up, they said.

The suspect spoke with the woman on Tuesday and threatened to kill her because she wanted to break up with him, sources said. The woman was being held in protective police custody yesterday.

Two neighbors, who asked not to be identified, said the woman often argued outside her home with the man, whom she had dated for nearly two years. Neighbors said the woman's father, Ezra Malcolm, disapproved of the relationship and did not let the man in his home.

"He'd always come by, but he never could go in," said a neighbor.

According to neighbors, six persons, all belonging to the same Jamaican family, lived at the house: Gordon, Blackstock, Malcolm, Malcolm's wife, and Malcolm's son and daughter.

The double slaying, plus the unrelated fatal stabbing of an unidentified man found yesterday brought the number of slayings in the city to 203, compared with 196 for last year, homicide detectives said. It is the highest number of homicides since 1981, when there were 234.

The stabbing victim, described as in his twenties, was found at about 2:40 p.m. in front of 2814 Pomeroy Place SE, police said. The man, whose identity was not released pending notification of his family, lived in the area, and was killed during an altercation with another man.