A 39-year-old mother of five was shot in the chest and killed outside her Northwest apartment door when she pointed a toy gun at an armed man early yesterday morning, according to family members and police.

The woman was identified as Diane Patricia Cook of 1429 Girard St. NW. Police say the brick apartment building is a well-known site for heroin sales. Family members gathered in Cook's sparsely furnished apartment yesterday afternoon said that Cook was not involved in the drug trafficking that surrounded her.

District police said they have no suspect and no motive in the slaying.

Cook's 12-year-old son Nathan said that a man knocked on the door about 1 a.m. and asked for a woman who did not live in the apartment.

"She closed the door and then he knocked again and she told him again that she did not know the woman he wanted," said Nathan as he rubbed his reddened eyes. "Then when he knocked a third time, she went and got a cap pistol and went to the door. That man, he was out there hollering. My mother opened the door and pointed the toy gun at him and he shot her."

Other family members confirmed Nathan's story. District police would say only that Cook had been killed in the hallway outside her apartment.

Clara (Chicken) Perrin, who said she was a girlfriend of Cook's brother Charles, said she and Charles Cook were asleep when the man knocked.

"Charles, he heard Diane arguing with someone and he stepped right on me trying to get out there to see what was going on," she said. "Then I heard a popping sound. I ran out there and Charles was by the door holding Diane in his arms. There was blood everywhere."

Perrin said she ran barefoot to the first floor to call the police because there was no telephone in the apartment.

Both Perrin and Ruth Young, a half-sister of Cook's, said that she was a quiet, soft-spoken woman devoted to her children.

"She was a little, tiny thing," said Young. "We grew up together and she was never one to argue. She had a hard time whomping the kids when they acted up."

Young said that Cook's husband, Luther D. Cook, died about four years ago and that Cook, who received Social Security payments, fell behind on payments on their house at 13th and U streets NW.

"She ended up at the Pitts [a hotel that the city leases as an emergency shelter] and she begged me to get her out of there and we got her this place," she said. "We were out last week looking for another place. She wanted to get out of here."

None of the neighbors interviewed on the fourth floor where Cook lived said they heard the argument between Cook and the man or the shooting.

A woman who lives across the hall showed a reporter a large bullet hole in her metal door. The woman, who did not want her name used, said police told her that the hole was made by a large-caliber bullet fired by Cook's assailant.

"The police woke me up about 1 o'clock and asked me if I had heard anything," she said. "They showed me the hole in the door but I had the TV on loud and didn't hear anything at all." The woman said that Cook was the third person slain on her floor in less than a year.

"I am devastated by all of this," she said. "And I am scared . . . . I wish I could move out of here."