Larry Viscidi, the 15-year-old Vienna youth charged with murdering his 12-year-old brother Billy, was released from police custody Monday and is staying at his home under is parents' supervision, a Fairfax County Juvenile Court official said yesterday.

The disclosure shocked and angered Viscidi neighbors who last week expressed relief that an arrest had been made in the case, described by authorities as one of the most bizarre deaths in recent Fairfax history.

"The fact that the boy is back home takes away all the piece of mind that came with the arrest last week," said one neighbor, whose sentiments were echoed throughout the suburban Virginia neighborhood.

Commonwealth's Attorney Robert F. Horan Jr. refusing yesterday to mention the accused by name because of the confidentiality provisions of Virginia juvenile law, said neighors in the southwest Vienna neighborhood have nothing to fear.

"I don't thing their children are in any danger," Horan said. The porsecutor, who last Wednesday night charged the youth with murder, said he would have preferred that "the juvenile" be kept in detention.

The youth was kept for five nights at the Northern Virginia Juvenile Detention Center in Lincolnia, according to Vincent M. Picciano, director of juvenile court services.

Picciano said the youth, according to a juvenile court order granting custody to Burton and I. Grace Viscidi, is to be kept "under controlled circumstances at his home." Piccano refused to elaborate.

Larry Viscidi, wearing a white T-shirt, was seen briefly yesterday afternoon inside his home at 503 Princeton Ter. Burton Viscidi, who works as a broadcast technician with Voice of America, was at home also. He refused comment on the provisions of Larry's release from custody.

Told by a reporter that Larry was back home, a nearby neighbor of the Viscidi's said, "Oh, is that going to have an impact around here. Everyone is afraid. I think it is just terrible."

The neighbor, who asked not to be identified, said the two months of publicity over the death of Billy, who was found buried in a plastic bag in his own back yard, "has made it uncomfortable to live around here.

"We can kiss goodbye in the next couple of years trying to sell our house if that kid (Larry) is going to be living around here."

Several neighbors asked yesterday if it is common in murder cases for accused juveniles to be released to custody of their parents.

Horan said it is common. He referred to the shooting death July 19 in the Mount Vernon area of 15-year-old Carolina Cordon, saying that the 15-year-old charged in that case was released to his parents under conditions similar to those in the Viscidi case.

Horan said "the juvenile" in the Viscidi case "will not be going to public schools until this case is disposed of one way or the other."

Under Virginia law, Larry Viscidi can be tried in Fairfax County Circuit Court if he is certified as an adult by the juvenile court. Horan said he is keeping "an open mind" on whether to request that the youth be tried as an adult.

The prosecutor said he will ask the juvenile court to make a study of "the juvenile's" sociological and psychological history. "When I look at the report, I'll make my decision," he said.

If the prosecution tries to have the youth certified as an adult, a juvenile court judge, in a so-called certification hearing, will decide whether the seriousness of the crime warrants transferring the case to Circuit Court.

Larry is scheduled for a preliminary hearing in juvenile court Oct. 10.

In the Vienna neighborhood, people who said they have known the Viscidi family frequently mentioned that the four Viscidi boys - Larry, Billy, Steve, 16, and Kenny, 10 - were often unsupervised at home.

"Those kids had the run of the house. They were all over the neighborhood and downtown (in nearby Maple Street in Vienna). I told my son not to play with them," one neighbor said.

Horan said the police investigation concluded, too, that the Viscidi children were poorly supervised.

"Even among the people in the neighborhood who said only good things about the Viscidi boys, the common complaint was that they were never supervised," Horan said.

I. Grace Viscidi, who told the minister at Billy's funeral in August that she thought her son's death was accidental, works as a computer programmer at the CIA.

Billy died on July 25 from a blow to the back of the head, Horan has said. Until his body was found buried in the back yard on Aug. 12, the boy was believed to have been a runaway or kidnap victim.