On a brick wall, in an alley off the worn 400 block of Kennedy Street in Northwest Washington, the code "4th KDY" is scrawled in blue spray paint. Down the block, in front of the bustling Kennedy Market, "4KDY" is etched in a patch of sidewalk.

The markings stand for Kennedy and Fourth Street. But they also have come to signify a horrific slaying. A similar symbol surfaced several miles away in Southeast Washington--carved on the back of Julio Guy Thomas, a 2-year-old boy found dead inside his home in the 700 block of Kentucky Avenue SE. The toddler, who had been beaten to death, suffered a puncture wound in his brain and a ruptured spleen.

"KDY4" also was found on a stuffed animal in the bedroom of a 12-year-old boy who had recently moved from the Kennedy Street neighborhood. Word that the boy had been charged with first-degree murder in the July slaying surfaced publicly after a pretrial hearing this month. The boy has been ordered to a shelter home pending trial. The next hearing in the case is set for Monday.

The Washington Post generally does not, as a matter of policy, identify juvenile offenders.

News of the toddler's death has appalled residents of Kennedy Street, focused unwanted attention on their neighborhood and sent police investigators searching for answers. Is KDY4, and its variations, simply a symbol of neighborhood identity and pride, or does it signify a gang? And if such a gang exists, did the 12-year-old murder suspect belong to it, and was the toddler's death related to gang activity?

"That's something we're looking very closely at right now," said D.C. police detective Lt. Alvin Brown.

But none of the residents and shopkeepers interviewed in the neighborhood--a hodgepodge of aging, two-story brick apartments and mom-and-pop stores--said they knew of a KDY4, or Kennedy and Fourth, gang or crew.

"Ain't no gang," one 13-year-old who lives in the 400 block of Kennedy said of KDY4. "It represents our block."

The teenager, like many others, could not believe that anyone linked to the block would commit such a crime. "I don't know nobody around here who would do that kind of violence, kill a baby," she said.

An employee of a convenience store in the neighborhood was also incredulous, though he allowed that some neighborhood residents aren't saints. "They fight with each other and shoot each other up, but I don't think they'll go to that extreme," said the worker, who declined to be identified. "They're not sick dudes."

The 400 block of Kennedy includes a fish market, a hair salon, beauty supply store and funeral home. It is also an artery for city buses, attracting people from around the neighborhood. Even in darkness, the street has a steady flow of traffic and pedestrians.

There's a certain pride to hailing from Kennedy. Some youths have been known to hang out in front of an apartment building, singing a song by a local go-go band that mentions the street. "These boys, they just be singing the song," said Tamika Bennett, 19, who lives in the block.

In recent years, crews have been a fixture up and down Kennedy Street between First and Ninth streets. Some have warred with one another, police say. Some members have lived in the neighborhood, at one time or another, but not necessarily on Kennedy.

The most notorious is the First and Kennedy Crew, which police say is a shadow of what it was before about a dozen of its leaders were imprisoned after they were indicted in 1995 on federal racketeering charges. The gang was linked to at least nine murders in the early 1990s, including the Nov. 22, 1994, slayings of a police sergeant and two FBI agents inside D.C. police headquarters.

"It was an urban, violent street gang, mostly young members who were involved in drug trafficking, who were motivated by money and status," said William Blier, an assistant U.S. attorney who prosecuted the gang.

The violence and crews have bolstered Kennedy's image as a tough place.

"I think younger kids try to use Kennedy Street to make them sound tough," said Gerald, owner of Talk of the Town Hair Gallery, on Kennedy near Fourth. A side of his brick building bears a spray-painted "4th KDY."

But Gerald, who didn't want his last name used, said he had not heard of a Fourth and Kennedy crew.

"It may be five or six kids who may have called themselves that, but as far as being organized, I have no idea," he said. And he, like others in the neighborhood, said they don't know the identity of the 12-year-old boy charged in Julio's death. Authorities have not released the youth's name because he is a juvenile. But a man who said he knows the boy's family said the youth had lived a few blocks off Kennedy.

Police speculate that if KDY4 is a crew, it is not very big. But they don't necessarily have to be. By definition, D.C. police Sgt. Jeffrey Madison said, a gang has "three or more people together that are aligned for criminal activity."

But police said they can't dismiss the possibility that "KDY4" simply symbolizes block pride.

Such neighborhood pride is evident at late-night go-go clubs, which play a hip-hop style of music unique to the District. Youths at the clubs often chant the name of their block or neighborhood, hold up signs or wear T-shirts bearing the name.

In its latest compact disc, "Skillet," recorded live, the local go-go band BackYard shouts out in its song "Life, Money, Struggle, Crime": "I like to thank that KDY." In the song "It's the Bomb," the band hollers out, "Ninth, Seventh, First, KDY."

Standing outside the Icebox night club off Bladensburg Road NE about midnight on a recent night, Terrance Cooper, the band's manager, said the songs don't recognize gangs but rather neighborhoods. By mentioning Ninth, Seventh and First, he said, the band covers that span of Kennedy.

"People come to the show. They have signs [of neighborhoods]. We call them out," he said.

Added Chris Burch, a promoter for the Icebox: "It's not seen as any type of gang thing. I think more than anything, it's more pride."

But gang or no gang, a father watches as his 15-year-old son hangs out at night with other youths in the 400 block. He's concerned that his son might get into trouble.

"You have people hanging around, you have people congregating," said the father, 49. "The police pass by. They don't give a damn."

He added: "We have incidents here. It's a hard street."

The man, who also asked that his name not be used, said he asked his son about KDY4 the other day.

"He says they say KDY simply because they live on Kennedy," the father said.

Some people along Kennedy complain about the negative publicity created by the killing. Sitting behind the counter at his hair salon late one recent night, Gerald complained about the notoriety that Julio's slaying has brought his stretch of Kennedy Street. Customers called his shop to mention that a 2-year-old had been killed in the Kennedy neighborhood.

"It wasn't here," he told them. "The actual incident didn't happen here."

"I don't know exactly what motivated [Julio's killer] to put that on the kid," he said. "But that's something that shouldn't be looked on our community as being bad."