The man accused of killing a 15-year-old girl last weekend in Northeast Washington "admitted to the shooting," prosecutors said in charging papers filed yesterday in D.C. Superior Court.

Joshua Ross, 20, told investigators that he promptly sold the gun used in the shooting that claimed the life of Myesha Lowe, a promising high school student who was to leave the next day on a group trip to Niagara Falls, the documents say.

Myesha, who police said was not the intended target, was sitting in a parked car with two friends when gunfire rang out just before midnight Saturday. She died Sunday afternoon at Howard University Hospital, the latest victim in a series of juvenile homicides this year in the District.

Federal marshals, working with D.C. police, arrested Ross on Wednesday morning in Hyattsville. Ross, who lived in Southeast Washington, was charged with first-degree murder. Yesterday, he appeared in court on the charge for the first time.

Police continued to search for two other suspects yesterday. They said they believe that the shooting stemmed from a long-running feud between young men from two Northeast neighborhoods -- one in the Trinidad section, which Ross was known to frequent, the other near 21st Street and Maryland Avenue.

One of the two women in the car with Myesha may have been the intended target, police have said, or the gunmen could have been aiming for a man who normally drives the vehicle.

Wearing blue jeans and a black Atlanta Hawks jersey, Ross was shackled at the waist during his court appearance, an unusual security measure that was prompted, the judge was told, by his "aggressive" behavior toward the marshals earlier in the day.

Ross's attorney, Tucker Carrington of the D.C. Public Defender Service, objected to the shackling, but Magistrate Judge Janet Albert deferred to the marshals.

Assistant U.S. Attorney Lynn C. Mattucci asked the judge to order Ross held without bond, and after reviewing the charging documents and hearing arguments from the two lawyers, the judge concurred.

Along with the admission that investigators said they obtained from Ross, both women in the car with Myesha identified Ross, according to the charging documents. One of the women said she was in the car, parked in the 1400 block of F Street NE, when a dark car pulled up, according to investigators' account.

The woman recognized the front-seat passenger as "Josh" from the Trinidad neighborhood, the charging documents say, and saw that "Josh," whom she later identified as Ross, and the back-seat passenger were aiming guns at them.

As the witness ducked, gunfire rang out, and Myesha was struck in the head.

The second surviving occupant of the car told investigators that when the dark car pulled up, Ross looked at her. Then, she heard the other woman tell her to "Get down," at which point, Ross and the other gunman opened fire, she told investigators, according to the charging documents.

She later identified Ross as one of the gunmen, the documents say.

In arguing that the government had not demonstrated enough evidence to sustain a first-degree murder charge, Carrington said it was unclear whether the two witnesses actually saw Ross open fire.

A third witness interviewed by police also placed Ross in the front passenger seat of the car on 14th Street NE.

She said gunfire erupted from the vehicle when it pulled alongside the car in which Myesha and the two women were sitting, the charging papers said.