A 19-year-old suspect in the killing of a popular waiter in Dupont Circle was arrested Wednesday night just moments after committing a robbery about 12 blocks from the slaying scene, D.C. police announced yesterday.

Officers staking out the neighborhood responded to a report of a robbery and apprehended Kurt Williams, who subsequently was charged with first-degree murder in the shooting early Monday of Adrien D. Alstad, 55.

Alstad was killed in the 1800 block of R Street NW during an apparent holdup, moments after leaving work at Annie's Paramount Steak House in the 1600 block of 17th Street. The killing unnerved residents of the tony Dupont Circle neighborhood, where a string of street robberies has taken place recently.

Residents said they were pleased to learn that an arrest had been made in the case. Last night, about 20 patrons at Annie's burst into applause when a police officer entered and announced the news.

"We're all very relieved," said Leigh Hendricks, the restaurant's manager.

Police said the break in the case came when a witness called police about 10:15 p.m. Wednesday to report a robbery in the 600 block of R Street NW. Officers rushed to the scene and arrested Williams and two juveniles at, and near, the Shaw Metro station in the 800 block of R.

Police recovered a pellet gun during the arrests. They charged Williams with robbery and the two youths, ages 15 and 16, as juveniles with robbery, authorities said. They were not charged in Alstad's killing.

During an interrogation yesterday, Williams implicated himself in Alstad's killing, police officials said.

Without Williams's statements, they said, it would have been difficult to bring charges in the case, because there were few witnesses to the killing, which occurred about 2:20 a.m. on a dark street.

Police have not recovered the murder weapon. They said they were continuing to hunt for others who might have participated in the killing.

At a news conference in front of police headquarters yesterday afternoon, Chief Charles H. Ramsey commended the witness who reported Wednesday night's robbery and quick-acting police officers. Without their work, Ramsey said, detectives would not have been able to make an arrest in the slaying.

"That robbery led ultimately to solving this case," Ramsey said.

Williams, of the 200 block of R Street NW, is scheduled to appear in D.C. Superior Court today for an initial hearing.

Last night, a relative of Williams's declined to comment. But Christine C. Leake, who lives at Northwest Cooperative Homes in the 200 block of R Street NW, said that the teenager had been living at the complex with his aunt for about three months.

"She couldn't control him," Leake said. "Kurt was nothing but a headache to her," often hanging around outside the apartments with people whom she described as bad influences. Last week, she said, Williams told his aunt that he had been pistol-whipped.

For days, police detectives had been poring through reports of robberies looking for links. They said several groups of robbers have been operating in the Dupont Circle area.

Police have stepped up patrols in the neighborhood, stationed plainclothes officers in shadowy areas and even had National Guard troops place high-powered lights to brighten dim streets.

Police and other officials said poor lighting encouraged the recent rash of robberies in the Dupont Circle and Logan Circle neighborhoods, particularly after bars close.

D.C. Council member Jack Evans (D-Ward 2), who represents the area where the killing occurred, said yesterday that residents were relieved that a suspect had been arrested.

He added that residents and employees and patrons of restaurants in the neighborhoods need to "be aware of your surroundings."

At Annie's yesterday, the mood turned from elation to somber reflection on the loss of a waiter who often helped friends and colleagues.

Tom W. Kelly, 67, said that about five years ago, he was losing his vision and didn't have money for glasses.

He said Alstad "walked me across the street and got me an eye examination. That was the kind of guy he was."

"See these glasses on my face?" Kelly added. "Adrien paid for them."

Judy L. Stouts, who trained Alstad as a waiter, said she was pleased by the arrest and wanted "revenge."

But she was still struggling to come to terms with the loss of her friend.

"This place will never be the same," Stouts said.

"They didn't kill a person," Stouts added. "They killed an angel."

Waiter Adrien Alstad, 55, was fatally shot in the Dupont Circle neighborhood.Waiter Adrien D. Alstad had left Annie's Paramount Steak House shortly before he was fatally shot early Monday in the 1800 block of R Street NW.