District police issued a description yesterday of a suspect in the fatal stabbing of Clarine Collier-Wilson, a 28-year-old Adams-Morgan resident who was attacked Tuesday evening as she walked home with her two young daughters.

Police said they are seeking a bearded black man at least six feet tall, who appeared to be in his late twenties or early thirties.

At the time of the slaying, witnesses said, the man was wearing a blue baseball cap, possibly with the letter "B" on the front, a light-colored T-shirt, a sweat jacket with blue sleeves and red and white patches on the front, and dark pants or jeans.

Collier-Wilson was stabbed to death about 6:40 p.m. on Lanier Place NW, around the corner from her apartment building on Harvard Street NW.

At the time of the attack, she was carrying her 3-year-old daughter in her arms while another daughter, 10, walked beside her.

Police said yesterday that robbery was being investigated as a possible motive. One official said Collier-Wilson's purse was missing when officers arrived at the scene.

As the investigation continued yesterday, a resident of Collier-Wilson's building told of rushing to the young mother's aid after hearing the screams of her 10-year-old daughter.

Imani Ali said he was standing in front of the building when he heard the child scream, " 'Someone's attacking my mommy! They're attacking my mommy! They're hurting my mommy!' " He said he ran around the corner and saw Collier-Wilson stagger and fall.

Ali said he and another man helped her up. At first, he said, he did not know the woman was wounded, but "then I saw the blood."

Ali said he tried to comfort Collier-Wilson as best he could. "I told her, 'Hold on honey. Hold on,' " he said. "But then I saw her eyes go back in her head."

Ali and other residents of the tree-shaded, hilly neighborhood said the killing has raised new fears about the safety of the area, on the northern edge of Adams-Morgan between 16th Street NW and the National Zoo.

Maurice Watson Jr., who lives in Collier-Wilson's building, said there has been a number of robberies and incidents of car vandalism in recent months. He pointed to a street light near Lanier Place and Argonne Place, about a block from where Collier-Wilson was killed. Watson said the light had been out since last summer, making it hard to see in shadows along that section of Lanier.

As detectives went door to door yesterday afternoon in search of more information, Collier-Wilson's family struggled with the tragedy that has left one of her daughters motherless and the other an orphan.

The father of Kamilla, 10, died in California last year. The father of Pareece, 3, who was divorced from Collier-Wilson about a year ago, lives in the District.

Yesterday, Collier-Wilson's sister, Janis Collier, said the ordeal has devastated the children. "My two nieces have gotten to the point where they don't want to talk to anybody," she said.

Collier said representatives from the Fielding Co., a Washington contracting firm where Collier-Wilson worked as a secretary, were making arrangements to start a fund to allow Kamilla to continue to attend a religious school in Northwest.

Last night, several detectives and five uniformed officers fanned out in the area in search of witnesses to the killing. One official said about 20 detectives had worked on the case throughout the day. Still, one official said the investigation was proceeding slowly. "Nobody knows nothing, nobody saw nothing, nobody heard nothing."

Staff writers Gabriel Escobar and Ruben Castaneda contributed to this report.