A 17-year-old Alexandria youth who frequented his old Southeast Washington neighborhood was charged yesterday with the fatal beating last month of an elderly Oakwood Street SE man, one of three killings on the street in which police have identified the teen-ager as the prime suspect.

D.C. police identified the youth as Gary Winston Jaggers of 245 Burgess Ave. Prosecutors said he gave police an 11-page statement in which he talked about the slaying he is charged with -- that of Burwell McLelland Davis, 88, on Dec. 16 -- and about the two other killings of elderly people on Oakwood Street. He was held at the D.C. Jail on a $500,000 bond.

The youth, charged as an adult, was described by friends and others as a troubled teen-ager who has a juvenile record dating back to his early teens. In addition to being the prime suspect in the three killings, police said they are investigating the youth in connection with numerous burglaries and assaults in the Southeast neighborhood.

The three killings on Oakwood Street, which occurred between late November and mid-December, so shocked the once-tranquil Congress Heights neighborhood just south of St. Elizabeths Hospital that some residents considered moving. Others had installed additional locks, were keeping to themselves and had become wary of strangers.

News of yesterday's 4:05 a.m. arrest came as a relief to residents. "It sounds like Christmas time to hear the news," said 24-year-old Larry E. Ward, who has lived on Oakwood Street for 16 years. "Maybe the neighbors will finally come back outside again. I feel like a stranger on the street."

D.C. Mayor Marion Barry, who attended a press conference held to announce the arrest of Jaggers, said he thinks the victims were assaulted because of their vulnerability. "He knew the neighborhood," the mayor said of the suspect.

Police said they arrested Jaggers as he slept in a vacant apartment in a largely abandoned public housing building at 3281 15th Pl. SE, which does not have water.

The arrest of the youth led City Council member Wilhelmina Rolark (D-Ward 8) to announce at yesterday's press conference that she is declaring "a war on vacant housing in Ward 8." She said these buildings have become "havens for criminals."

Martha Russell, who also lives in the condemned building where Jaggers was arrested, said the youth grew up in Southeast Washington. Although his family now lives in Alexandria, Jaggers spent most of his time in Southeast, Russell said. "He was like one of my own," Russell said. "He and my children grew up together."

She said police yesterday took several items of Jaggers' clothing and a ring that the youth gave her as a Christmas present as evidence. She said police also took a pair of shoes the youth allegedly wore in the beating of one of the Oakwood Street victims. Deputy Police Chief Alfonso Gibson said police have gathered "physical evidence" linking the youth with the killings and other incidents, but declined to identify the items.

"I'm just so sorry this has happened," Russell said, as she stood beside her two large german shepherd dogs in the doorway of the building. "This thing has taken a lot out of me."

A school official who remembered Jaggers from his days at Johnson Junior High School, located at Bruce and Robinson Place SE, said the youth's "attendance in school was poor. For that reason, his grades were poor." The official said the youth did not complete the seventh grade.

Assistant U.S. Attorney Richard W. Goldman told Superior Court Judge William S. Thompson that Jaggers has a lengthy juvenile record. In 1978, Jaggers was found guilty of two counts of attempted robbery, Goldman said. Jaggers also pleaded guilty to an attempted petit larceny. Another robbery charge was dismissed, the prosecutor added.

The youth was committed in 1978 to Cedar Knoll, the city's juvenile detention facility. He escaped shortly thereafter, Goldman said.

Jaggers appeared in D.C. Superior Court in August 1980 on a robbery charge. However, he gave a false name to Superior Court Judge Margaret A. Haywood, so the judge was not aware that he was a runaway from a juvenile facility, Goldman said. The teen-ager was released on personal recognizance. f

When the youth did not appear for a scheduled hearing, Haywood issued an order for his arrest, but he was not found until yesterday.

The other two Congress Heights murder victims were Marie Schneck, 81, of 421 Oakwood St., who was bludgeoned on Nov. 17 and died five days later in a hospital, and Julia A. Gambrill, 65, who was fatally beaten in her ransacked home at 227 Oakwood St. on Dec. 12. Davis, the third murder victim, lived at 445 Oakwood.

In addition to the murder charge in Davis' death, the youth has also been charged with burglary in connection with the Dec. 19 housebreaking at 2403 Irving Pl. SE, also in Congress Heights.