A Washington man stabbed his wife and five-year-old son to death in an Alexandria apartment Saturday afternoon, and then killed himself with a knife, Alexandria police said yesterday. The three bodies were discovered at about 5:30 p.m. by a family friend who lived in the apartment.

Police said that 33-year-old Anne T. Winton and her husband, Marcos Kusanovic, 34, apparently had been involved in a series of disputes when Winton and their son, Alex Kusanovic, left their home at 5114 Sherrier Place N.W. early Saturday morning and moved in with friends in Alexandria. Police said Kusanovic later followed her to the basement apartment at 5473 Sheffield Ct. in Alexandria's West End, where the killings took place.

Kusanovic had been a self-employed construction worker, doing most of his business in Arlington, according to Det. Wayne Robey who is heading the investigation. Until recently, Winton had been a student at George Washington University. Robey said that friends of Kusanovic and Winton told police that the couple had been involved in several domestic disputes.

A resident of the sprawling complex of garden apartments known as the Hamlets, scene of the murder-suicide, said that she was watching television at about 5.30 p.m., when the tenant of the basement apartment beneath "came running out close to the building, saying 'Help!'"

The woman, who asked not to be identified, said she believed that the tenant also was a student at George Washington University and knew Winton.

Police officer Arthur Miller was investigating a burglary in the area at the time, police said, and found the bodies in the apartment.

Yesterday afternoon, as detectives went through the small, two-story gray house on Sherrier Place, just off MacArthur Boulevard, where the Kusanovic family had lived, nearby residents said they knew little of the family who had lived on the quiet, treelined street for about a year.

Susan Sechler, who lives next door, said that while most people in the neighborhood knew each other, the Kusanovic family kept to itself. Kusanovic never greeted her she said, until yesterday morning when "he seemed elated."

"We always said 'Hi' to him, and yesterday was the first time he said 'Hi' to me," Sechler said. She said that Kusanovic and his wife seemed to dote on their child. "Just two days ago, I saw him with the boy sitting on his knee. They seemed so loving toward the little kid."

A Washington doctor who had employed Winton as a part-time secretary last year said that he and his partner met her about a month ago and tried to get her to return to her former job. But the doctor, who asked that his name not be used, said Winton told them she was now working at the Folger Shakespeare Library.

"She said she had split up from Marcos, and that he had the child," the doctor said. But she seemed confident that things would work out, he added. "She wasn't worried," he said. "She was very upbeat."

Results of the autopsies are scheduled for today, said Robey, adding that death by "self-inflicted knife wounds" is "unusual, but it happens."