District police had been looking for 16-year-old Marcel Merritt for months. They found him at 3:30 a.m. last Monday, fatally shot and lying on the Suitland Parkway in Southeast Washington.

Since then, authorities have described the Southeast teenager as a neighborhood terror. Merritt is suspected in the killings of four people and the critical wounding of another over 20 months, starting shortly after his 14th birthday -- all while he was supposed to be under the supervision of the D.C. juvenile justice system.

Merritt came to the attention of police in February 2004, when he was picked up while driving illegally and carrying a submachine gun and a pistol. For a time, he was held in the city's Oak Hill juvenile detention center in Laurel and then released to the care of a relative. By August, the city had lost track of him.

Police detectives said they had suspected Merritt in a series of homicides, robberies, assaults and shootings but were not able to gather enough evidence to charge him with those crimes. His reputation for violence made witnesses afraid to come forward, they said. Only after his death are detectives getting the cooperation they needed to uncover the extent of his activities, investigators said.

Since Merritt's death, police closed investigations of two homicides that they have said he committed and are pursuing leads in the other homicides. One of the closed cases took place in April 2004 -- just two months after D.C. police caught Merritt with the Mac-10 submachine gun and semiautomatic handgun. Last year, he was arrested on another gun charge. This year, he was arrested in a stolen car, authorities said. Law enforcement officials would not provide details on the arrests.

Because records involving juveniles are confidential, it is unclear how the courts and the D.C. Department of Youth Rehabilitation Services dealt with Merritt. He was deemed to be an "absconder" after he disappeared from the home of his aunt sometime before Aug. 5, authorities said, and an order was issued for his arrest.

Those who mentored and worked with Merritt said he should have been kept in the juvenile detention facility or placed in a strict residential program far from his neighborhood in the 600 block of Atlantic Street SE, a stretch of red-brick rowhouses in the Washington Highlands area. They said that as recently as this summer, they urged officials with the youth services agency not to send him home.

"I told them that it wasn't a good idea to release him," said Ronald L. Moten, a director at Peaceoholics, a nonprofit group that worked closely with Merritt over the years. "There were a lot of things going on on the street. . . . He needed more rehabilitative treatment."

Another director at the program, Jauhar Abraham, said, "You can't put him back into the projects that breeds this stuff and think he's going to be all right without the appropriate services from agencies."

Two years ago, the city promised to step up efforts to find youths who escape from the juvenile justice system. That pledge came amid reports that dozens of juvenile escapees were committing crimes -- or getting killed -- while on the run. Officials with the youth services agency said the number of "absconders" has fallen about 50 percent over the past two years.

Merritt's body was found Monday on the parkway near Alabama Avenue, along with that of a friend. Both bodies had been shot a number of times. The friend, Kevin A. Jackson, 17, has not been tied to any of the homicides, police said. No one has been arrested in their slayings.

Officials with the youth services agency said they attempted to find Merritt after they realized he disappeared in August, but they would not discuss other aspects of his case, including why or when he was released from Oak Hill.

In an e-mail statement, the department's director, Vincent Schiraldi, wrote: "Over the past nine months, we've been working diligently every day to reform operations and improve programs here. Tragically, in this case, those reforms didn't come quickly enough so now we must redouble our efforts to make sure this kind of tragedy doesn't happen again." Schiraldi became head of the agency in January.

Merritt's family declined to comment during reporters' visits to their home last week. His mother, Tameka Merritt, 34, has a history of convictions over the years for crimes including drug offenses, theft and solicitation. She is in a federal prison, authorities said.

Law enforcement officials now have said that when they arrested Merritt on Feb. 3, 2004, Merritt was about to seek revenge for the death of a friend, James Richardson, 17, who had been fatally shot at Ballou Senior High School a day earlier. At the time of his arrest on the gun charges, police officials said, Merritt -- who was not identified publicly -- might have been involved in a feud that led to Richardson's death.

Moten and Abraham said Merritt was at Oak Hill for at least several weeks after that arrest.

On April 22, 2004, police said, Merritt allegedly committed his first killing -- shooting Andre Lampkin, a 26-year-old car detailer, in the block where Merritt lived.

Within a few weeks, police focused on Merritt as a suspect, but they said no one was willing to come forward to identify him.

The next killing tied to Merritt was less than six months later, when one of his close friends was shot in a stolen car. Informants told police that Merritt had shot Shawn J. Riley, 15, but detectives could find no eyewitnesses, officials said. Police would say only that the motive for the shooting was related to the car or its contents.

After witnesses to those killings spoke last week, police closed investigations into both homicides -- officially naming Merritt as the suspect in the deaths of Lampkin and Riley.

Merritt was arrested a second time in 2004 on another weapons offense. At some point after Riley's slaying, Merritt was sent back to Oak Hill, according to Moten and law enforcement officials.

He was released in the spring and vanished. In May, a judge issued a custody order -- or juvenile arrest warrant -- because he was violating the terms of his release, law enforcement officials said. Merritt was then arrested in Maryland in a stolen car -- the charges were later dropped -- and sent back to Oak Hill, according to Moten and Abraham.

Moten and Abraham, who were mentoring Merritt at Oak Hill, said it was about this time that they urged the Department of Youth Rehabilitation Services not to send him home. But he was released to the custody of his aunt sometime this summer, according to Moten and Abraham.

Law enforcement officials said a second custody order was issued Aug. 5 because social workers could not find Merritt.

By then, investigators had found at least one witness tying Merritt to Riley's killing, police said, and they were eager to question him. Two days after the custody order was issued, detectives distributed fliers to patrol officers to arrest Merritt if they spotted him. The police department's warrant squad was also looking for him.

As police were searching, two more killings occurred. Michael Lanham, 32, was fatally shot Sept. 17 in the 1300 block of Barnaby Terrace SE. Five days later, Gregory Sam, 41, was killed nearby.

The motives for these homicides are not clear, but police officials said that they believe Merritt killed both men and that they expect to close those investigations soon. Investigators are reviewing homicide and assault files to see whether there might be other connections to Merritt, they said.

Merritt's last suspected crime occurred Sept. 27, the officials said. Early that morning, he allegedly shot and critically wounded Cheryl Stover, 38, police said. Merritt had lost money to Stover in a craps game, the officials said, and he wanted his money back.

Stover remains hospitalized. Her mother, Annie Stover, 70, died days after the shooting after suffering a heart attack.

"My wife had a weak heart," said her husband, Melvin Stover, 70. "The shooting upset her."

Melvin Stover said he felt that Merritt's death might have cheated him out of seeing justice done in his daughter's shooting. "I wanted my daughter to get well enough to point him out so police could get him," he added. "I would rather see him in jail than dead."

Although police had difficulty finding witnesses willing to testify, relatives of Lampkin and Riley said they have long believed that Merritt was responsible for the killings.

Lampkin's mother, Henrietta Green-Fairnot, said she was told several months after her son's death that Merritt had been the gunman. "It is truly sad," she said.

Riley's mother, Cornelia Robertson, said she began visiting the Atlantic Street neighborhood this spring and summer to learn who might have killed her son. She said residents told her that Merritt was responsible.

As she wandered through the neighborhood one day, Robertson spotted Merritt walking toward her. He gave her a big hug, she said.

"That felt really funny," she said. "He caught me off guard. I knew he had killed my son, but I didn't want to show it."

Staff writer Nia-Malika Henderson contributed to this report.

D.C. police believe that Marcel Merritt (not pictured) killed Michael Lanham, left, and Gregory Sam, second from left, in September and expect to close those investigations soon. Witnesses came forward last week to link Merritt to the April 2004 slaying of Andre Lampkin, second from right, and the October 2004 killing of one of Merritt's close friends, Shawn J. Riley, right. Police closed the Lampkin and Riley cases last week.