D.C. police arrested a 20-year-old man yesterday in the slaying of a teenager last weekend and said that the shooting probably stemmed from a feud between two neighborhood groups.

Detectives are seeking at least two other men in the shooting of Myesha Lowe, 15, police officials said. Myesha was shot late Saturday as she and two friends sat in a car in Northeast Washington, apparently an unintended target in a months-long dispute, police said.

Joshua Ross was arrested at 10:20 a.m. yesterday at a friend's home in the Hyattsville area. Ross, who lived at several addresses in the District, was jailed on a charge of first-degree murder.

D.C. Police Chief Charles H. Ramsey yesterday condemned those responsible for the city's violence, declaring: "Ross and people like him must be dealt with as harshly as possible. In D.C., that means life in prison without any possibility of parole. He and others like him that gun down people on the streets of our city are a menace to society and deserve no pity or mercy as far as I'm concerned."

"You get sick of these guys," Ramsey added. "It's just absolutely crazy. They care nothing about life at all. Why should we care about theirs?"

When the killing occurred, police had a warrant for Ross's arrest for running away from a group home in Northwest, authorities said. The warrant was issued in September.

In March 2002, Ross, then 17, was sentenced to the custody of the city's Department of Human Services to receive care and rehabilitation. He had arrests as a juvenile for driving a stolen vehicle, receiving stolen property and a weapons offense, according to confidential records.

Police officials said that Ross had lived in several residences in Northeast and that he was known to frequent the Trinidad neighborhood. They said his arrest came after police got help from witnesses and community members. A witness identified Ross as one of the assailants after viewing an array of photos, investigators said.

Detectives spent much of Tuesday trying to arrest Ross on the murder warrant but were unable to locate him until yesterday, when they found him in the 5000 block of 56th Street in the Hyattsville area. Ross is expected to appear today in D.C. Superior Court.

Investigators were working round-the-clock to find the other two suspects, police said. Detectives also were seeking a black Crown Victoria seen leaving the scene of the shooting. Three men were spotted in that car, police have said.

Police officials said the shooting probably stemmed from a long-running dispute between groups of young men in Trinidad and the neighborhood surrounding 21st Street and Maryland Avenue NE.

Authorities said police have connected the dispute to several shootings. The feud also could be responsible for at least one homicide, they said.

The assailants Saturday night -- believed to be men from the Trinidad neighborhood -- spotted the car that was occupied by Myesha and her two adult friends in the 1400 block of F Street NE, police said. The gunmen either walked up to the car or opened fire as they drove past about 11:45 p.m., police said.

The gunmen either were trying to shoot a man from the 21st Street neighborhood who normally drove the vehicle or were trying to kill one of his friends in the car, investigators said.

Ramsey said the motive behind the slaying was consistent with many other shootings his department has investigated.

"You can almost come to expect this," said Ramsey, who credited hard work by detectives for the arrest. "This is just the way of life on the street, the rules they live by. . . . There is a culture of violence that exists in many of our communities."

Cmdr. Jennifer Greene of the 5th District, whose officers patrol the area where the feuding neighborhood groups are, said she was deploying extra police in the areas to stop violence. She also said officers were gathering intelligence to determined whether "this ongoing feud is at peace or whether there is still something that could flare up."

Greene said the dispute between the groups had been relatively calm in recent months.

Myesha Lowe's family expressed relief at the arrest but anger at the motive. "We don't have anything to do with what they do," the teenager's mother, Francine Lowe, said of the feud. "That's what makes me angry. It's always the innocent ones that get killed. You are putting innocent lives on the line."

Staff writers Nicole Fuller and Sewell Chan contributed to this report.