WASHINGTON, Oct. 26 - With a loud crack and a blinding light of the SWAT team's disorienting but harmless "flash bang," the agents rushed the blue Chevrolet Caprice parked in a highway rest stop in rural Maryland. They smashed out several windows and unlocked the doors. Within seconds, the agents pulled the two dazed occupants from the car at gunpoint and placed them under arrest.

The police had feared a bloody end to their 23-day manhunt. But the peaceful arrests of John A. Muhammad, a 41-year-old Army veteran, and his 17-year-old companion, John Lee Malvo, brought an abrupt coda to an investigation full of dead-end leads and missed opportunities, followed by a rapid reversal of fortune.

The two men who the police now say are the snipers, who had communicated by phone and letter with declarations like "Call me God," were discovered asleep at the wheel, literally. Behind the front seat, the police say, detectives found a long white box holding a Bushmaster XM15, a high-powered, deadly accurate weapon capable of firing .223-caliber bullets. By nightfall on Thursday, ballistics evidence tied that rifle to 11 of the area's 13 sniper shootings.

Charles A. Moose, the police chief in Montgomery County, Md., who led the investigation, said in an interview that police work takes persistence, teamwork and community support but almost always depends on chance.

"As police chief, I know you need a lot of luck," Chief Moose said. "I'd like to think it's all skill and moxie and brains. But it's mostly luck."

After the arrests, computer records showed that the police in his county, in Baltimore and in Washington had encountered the suspects' car on at least 10 occasions but did nothing; the car was legally owned, Mr. Muhammad had no criminal record that showed up in the government's database, and everyone was fixated on a white van, not a blue Caprice.

In the end, the investigation turned on a series of cryptic communications between the sniper and the police. "You are dancing with a guy and you know the lights are out and you don't know where the edge of the dance floor is," one senior government official said in an interview earlier this week.

Mr. Muhammad and Mr. Malvo were charged on Friday with six counts of first-degree murder in Maryland, where the authorities said they would seek the death penalty against Mr. Muhammad. Additional murder charges are expected to be filed against Mr. Muhammad and Mr. Malvo in Virginia and in the District of Columbia, where other killings took place.

The two men were also charged on Friday with a murder-robbery in Alabama that helped the authorities solve the sniper shootings here.

The hunt for the sniper became a vast murder mystery in which the police enlisted the support of the capital area's five million citizens and communicated with the killers in coded messages carried by the news media. Law enforcement officials said they did not yet know whether the sniper heard any of their messages. Each of the five police statements to the killer was the product of intensive discussion between Chief Moose and his chief federal partners in the case, Michael R. Bouchard of the Baltimore office of the Bureau of Alcohol, Tobacco and Firearms and Gary M. Bald of the Baltimore office of the Federal Bureau of Investigation.

The three men described the turning points in their investigation in an interview on Friday. They sat at the same octagonal wooden table in Chief Moose's quiet corner office where they had drafted and debated the unusual messages delivered by Chief Moose to the killers.

"I'll talk to the devil himself to keep another person alive," Chief Moose said.

Every word in his statements was evaluated by experts in serial killings, crisis negotiation and criminal behavior.

Each message carried enormous risks. If the language was too confrontational, it could provoke the sniper to kill again. If the statement was too conciliatory, it could lead the sniper to conclude that the authorities did not take them seriously, with equally deadly results.

"You try to get a little control over the clock, build credibility and trust, and force the sniper to make a mistake," explained an official involved in the investigation.

The Montgomery County Police Department was backed by the largest investigative team ever assembled for a local murder case in the United States. Advanced military spy aircraft patrolled the skies, police barricades stranded drivers on dozens of gridlocked highways, and an army of thousands of law enforcement personnel chased 16,000 leads culled from more than 100,000 phone calls to a telephone tip line.

Each day, President Bush (news - web sites) was briefed on developments and worried aloud about what he said was "a ruthless person on the loose." News accounts of coordination lapses brought Congressional pressure on the F.B.I. to take over the case. In the end, almost every expert's best guesses about the suspects, their vehicle and their motives turned out to be wrong.

Even now, the suspects' motives remain unclear. Neither man has cooperated with the authorities. Some officials dismiss the sniper's $10 million demand, made in a letter left at the scene of one of the shootings, as nothing more than a way to rationalize the killing rampage.

At the heart of the case was a dialogue between the cops and the killers angry threats from the sniper were matched by tentative, carefully worded responses from the authorities filtered through the news media.

The frustration encountered in communicating with the authorities may have spurred the sniper to kill again, according to the notes said to have been from the killers. But each missed call also provided the police with an unanticipated opportunity to get new evidence, as the sniper, in what appeared to be mounting rage, tried to get the attention of the authorities by reaching out to others. In a fateful call last weekend to a priest in Ashland, Va., the police say the sniper handed them a crucial clue.

Possibly as a way to establish his credibility, the sniper bragged of a crime in Montgomery, Ala. The next day, the police discovered an unsolved murder-robbery on Sept. 21 at a liquor store in Montgomery in which an unmatched fingerprint was left behind on a magazine about guns. The print belonged to Mr. Malvo, and the discovery quickly led the authorities to Mr. Muhammad and the Caprice.

Without the print, the authorities concede, the investigators cannot say how much longer their investigation would have dragged on or how many more lives might have been lost.

The Phantom White Van

The first shot offered little hint of what was coming. A single bullet sliced through the front window of a Michaels craft store in Montgomery County at 5:20 p.m. on Oct. 2. No one was hurt. Forty minutes later a single shot fired from a high-powered rifle killed James D. Martin, 55, a program analyst shopping for church groceries, in a supermarket parking lot in Wheaton, Md.

Early the next morning, Oct. 3, the sniper struck with spectacular fury:

At 7:40 a.m., James L. Buchanan, 39, was shot in the chest and died as he mowed a lawn near a shopping mall in Rockville, Md.

At 8:10 a.m., Premkumar A. Walekar, 54, a taxi driver, was shot and killed at a gas station in Aspen Hill, Md. within a mile of the earlier shooting.

At 8:40 a.m., Sarah Ramos, 34, an immigrant from El Salvador (news - web sites) who worked as a housekeeper, was shot in the head while sitting on a bench outside a Montgomery County post office. A witness reported a white truck speeding from the scene, starting off a futile hunt for the mysterious vehicle.

At 10 a.m., Lori Ann Lewis-Rivera, 25, a nanny from Idaho, was killed as she vacuumed her van at a gas station in Kensington, Md.

At 9:20 p.m., Pascal Charlot, 72, a retired carpenter who had immigrated from Haiti, was shot dead near a bus stop in northeast Washington. A witness reported seeing a beige Chevrolet Caprice flee the scene. The Washington police did not release information about the Caprice until four days after the shooting, but the report was discounted as the search for a white van gained momentum.

One official said that the suspects failed to arouse police suspicion because they did not fit the beliefs that were already forming in the case. "Everyone thought we were looking for an angry white guy in a white van," said a senior government official. "Instead, it was really two black guys in a blue Chevy. We got stuck on that white van."

The next day, Oct. 4, an unidentified 43-year-old woman was shot in the back as she loaded shopping bags outside a Michaels craft store in Fredericksburg, Va., about 50 miles south of Washington. The woman was taken to the hospital and survived.

The carnage was stunning. Chief Moose confirmed that each of the dead had been shot with the same .223-caliber weapon.

"People are very nervous, very anxious," the Montgomery County executive, Doug Duncan, said, adding that high school football games would be held as scheduled as a sign of determination to maintain community life.

In most large criminal investigations, local authorities are reluctant to ask for help from federal law enforcement agencies it is seen as bad for morale, and many local police officers resent the F.B.I.

Quietly, Chief Moose had asked for federal assistance even as some in his department wanted to conduct the investigation without outside aid.

"Local law enforcement asks for help from federal law enforcement with a lot of hesitation," Chief Moose said. "We've got to get past it. Hopefully, there is a lesson here that it can work. I might still have people dying because I could not resolve my issues with the feds."

The F.B.I. and A.T.F. arrived with their first teams of agents along with a computer team to organize the information that was beginning to pour in to the Montgomery County police. The investigation was housed in a building across the street from Montgomery County police headquarters on three floors of office space rented by the F.B.I. under an emergency procurement arrangement. Back at the F.B.I.'s Washington office, agents set up a telephone tip line to handle the thousands of calls coming in. Hundreds of people called in claiming to be the sniper, and later on, investigators struggled to determine which calls had actually been placed by the sniper. On Oct. 21, a full moon, crank calls to the tip line spiked.

"A lot people would be calling who would say some bizarre things on the phone," Mr. Bouchard of the A.T.F. said. "Some people would just say a few words and hang up. It was difficult to assess what they said and what they meant."

Of the three commanders as Chief Moose, Mr. Bouchard and Mr. Bald were known it was Chief Moose who had the most practical experience in violent crime. Mr. Bouchard, an arson and explosives specialist, said that he knew little about ballistics.

Mr. Bald had recently taken command at the F.B.I.'s Baltimore office. Before that he headed a Boston investigation of a former F.B.I. agent who was convicted of helping organized-crime leaders who had been his confidential informers. "We got along great," Mr. Bald said of his relationships with Chief Moose and Mr. Bouchard. "There was never a situation of a tug of war between us."

The Tarot Card and the 'Act'

On Monday morning, Oct. 7, the sniper's tactics grew even more ominous. A 13-year-old boy, whose name has not been made public, was shot in the chest as he walked into a school in Bowie, Md. The shooting, the first in which the sniper attacked a child, led school districts to ban outdoor activities.

In a wooded area near the school, the police found a tarot death card, scrawled with the words, "Mr. Policeman, I am God." When a television station broadcast a report about the card and the cryptic message, Chief Moose lashed out at news organizations. But it now appears that his anger may have been at least partly an act, in which the sniper was his intended audience.

Mr. Duncan, the county manager, said the card also had another message, instructing the police not to release it to the press. As a result, when Chief Moose lashed out at the news media, he appeared upset, an impression he wanted to convey to the sniper, according to Mr. Duncan, so he would not think his orders were violated.

"Some of the anger toward the media was to separate himself from whoever leaked that card," Mr. Duncan said. "That was a real communication link and we basically felt that if that communication had been severed the anger toward the media really was a message to the shooter."

As the authorities' attention remained focused on the white van, the police in Baltimore had an encounter on Oct. 8 with Mr. Muhammad, who was found sleeping in a blue Chevrolet Caprice parked on a side street. The police apparently found nothing suspicious.

With six dead and two wounded, the toll climbed again a week after the shootings began. At 8:20 p.m. on Oct. 9, Dean Harold Meyers, 53, a civil engineer from Gaithersburg, Md., was fatally shot in the head at a gas station in Manassas, Va., about 30 miles southwest of Washington. The police said that a white van was seen leaving the scene.

Two days later, Kenneth H. Bridges, 53, of Philadelphia was shot and killed as he pumped fuel into his car at a gasoline station near Fredericksburg.

Investigators raced to the scene and scoured for evidence. "You leave a note and I want to suck everthing out of that," said one investigator, describing his approach to the case. "You make a call or you kill somebody everything that happens we learn something, and if they make a mistake we can get ahead of them."

One of the F.B.I.'s Own

But the killer struck again, this time on Columbus Day. At 9:15 p.m. on Monday, Oct. 14, Raymond Massis, of Falls Church, Va., drove into the parking lot of his local Home Depot, at the Seven Corners Shopping Center. From his car, Mr. Massis said, he heard a "loud snap." He jammed on his brakes and watched people run toward a woman lying face down on the pavement.

The victim was Linda Franklin, a 47-year-old F.B.I. intelligence analyst, who, with her husband standing beside her, had been loading shelves into the trunk of her car for a new home. At the time of Ms. Franklin's death, 400 F.B.I. agents and support employees had been assigned to the case. A week later, the number had grown to 900, and at the end of the investigation, more than 1,000.

After the shooting, the Fairfax County police said they were searching for a cream-colored Chevrolet Astro van with a broken left taillight. The police set up roadblocks on the major highways, stopping and searching dozens of white vans. Traffic was gridlocked in Northern Virginia until long past midnight.

Matthew M. Dowdy, 37, reported seeing an "olive-skinned man" step out of the Astro van and fire a single shot from a weapon that he said was most likely an AK-47 assault rifle. Mr. Dowdy's statement was later found not to be credible, officials said. He was charged with providing false information to the police.

By then, however, it was too late the information about a Chevy Astro van produced thousands of tips from motorists all over the region, law enforcement officials said. There had already been sightings of a white van, and the authorities had released composite sketches of a white box truck and a white van.

"Everyone was looking for white-van drivers," Chief Moose said in an interview. "We had two drivers of white vans come forward who were at shooting scenes to say, `I was there, but it wasn't me.' "

Ms. Franklin's shooting brought a fresh wave of despair. She was dead and the investigative team had failed to catch the killers. "This investigation was a roller coaster, but we were always optimistic," Chief Moose said. "It had its ups and downs."

The Two Montgomerys

On Thursday, Oct. 17, a man claiming to be the sniper called the public information officer for the Montgomery County police, saying, "I am God." Officials described the call as lasting three minutes and said the caller was extremely angry. "Don't you know who you're dealing with?" the caller demanded.

The caller also made a reference to a crime in "Montgomery," apparently as a way to gain credibility with the listener. The officer who took the call assumed that the sniper was referring to the shootings in Montgomery County, officials said.

The next day, Oct. 18, the sniper spoke with a priest in Ashland, Va., Msgr. William Sullivan, the pastor of St. Ann's Church. "I am God," the sniper said. But this time, the sniper referred to a crime in "Montgomery, Alabama." He said Alabama repeatedly, according to the Rev. Pasquale Apuzzo, secretary to the bishop at the Roman Catholic Diocese of Richmond, Va. The monsignor did not report the phone call to the police, thinking it was a prank call.

The longest lull between shootings five days occurred after the Home Depot murder. The authorities say they believe the lull was attributable to the sniper's frantic efforts to contact them to make a ransom demand.

At 8 p.m. on Saturday, Oct. 19, a 37-year-old man was shot in the abdomen while walking to his car with his wife after dinner at a Ponderosa Steakhouse in Ashland. The shot appeared to have come from a wooded area about 300 yards west of the Interstate 95 entrance ramp.

In the woods, tacked to a tree, the police found a four-page letter that was wrapped in plastic. It was the second written communication from the sniper.

On the cover sheet was written, "Call me God," along with "For you, Mr. Police" and "Don't Release to the Press," according to senior law enforcement officials who have seen the document.

The letter demanded $10 million to be wired to a stolen platinum Bank of America Visa credit card, whose 16-digit account number and PIN number were included.

"We will have unlimited withdrawal at any A.T.M. worldwide," the letter said.

The letter harshly criticized the authorities as making it hard the sniper to contact them to begin ransom negotiations. The letter denounced the operators of the sniper telephone tip line, which one of the suspects called at least four times, officials said. It described the operators as incompetent and said officials mistook the calls "for a hoax or a joke." "Your failure to respond," the letter said, "has cost you five lives." The note had this chilling postscript: "Your children are not safe anywhere at any time." The letter also asked the authorities to contact the sniper at a phone number at 6 a.m. on Sunday.

But law enforcement authorities said they missed the phone call because they said there was a problem with the number that had been provided. On Sunday, at 7:10 p.m., Chief Moose issued his first direct contact to the sniper through the news media. "To the person who left us a message at the Ponderosa [Saturday] night, you gave us a telephone number," Chief Moose said. "We do want to talk to you. Call us at the number you provided."

A person involved in the investigation said that the police believe the sniper called again, and the number for this call was traced to an Exxon gas station in suburban Richmond. Within minutes, the police, armed with automatic rifles, surrounded a white Plymouth Voyager parked next to a public telephone. Two men were taken into custody, and the Voyager was towed away. The event was broadcast live on the cable news channels.

A clue that the arrests made that morning had not captured the sniper was revealed by Chief Moose. At 10 a.m., while the cable news channels continued to report hopefully about the men in custody, Chief Moose stood behind the podium and delivered his second announcement: "We are going to respond to a message that we have received. We will respond later. We are preparing that response at this time."

The authorities knew the sniper was angry from the earlier phone conversation. That message by Chief Moose was an effort to placate the sniper.

The arrested men, one a Mexican immigrant laborer and the other a Guatemalan immigrant laborer, were later found to have no involvement in the shootings. They were turned over to the Immigration and Naturalization Service for deportation.

What was not known that morning is that the police had missed the sniper, in that Exxon parking lot, by a matter of minutes, investigators said.

"It was a trap that closed too quickly," a government official said.

"The huge police presence did not move quickly enough," the official said. "They were almost heroes."

Final Killing, Final Demand

The sniper sent another message, just after dawn the next day with a shooting and another note left nearby. Conrad E. Johnson, a 35-year-old bus driver, was shot with a single bullet as he stood in the doorway of his bus shortly after 6 a.m. on Tuesday, Oct. 22, near Silver Spring, Md. The note reiterated the threat to children.

Still frustrated by an inability to contact the leaders of the investigation, the sniper in this note asked for a private 800 number to use to call the authorities directly.

At 7:15 that evening, Chief Moose again addressed the sniper, saying that it was "not possible electronically to comply" with his demand for $10 million to be wired to his bank account. "However," Chief Moose continued, "we remain open and ready to talk to you about the options you have mentioned. It is important that we do this without anyone else getting hurt."

Meanwhile, detectives in Montgomery County had received the file from the unsolved killings at the Alcoholic Beverage Control Board's Store No. 5 in Montgomery, Ala. The unknown fingerprint, from the gun magazine, was run through the F.B.I. database, and it matched that of Mr. Malvo, a Jamaican who was taken into the custody of the Immigration and Naturalization Service in Seattle last December. Mr. Malvo admitted that he was in the country illegally and had entered with the help of smugglers from Haiti to Florida. He also said he lived in a shelter with John Allen Muhammad, whom he described as his stepfather.

Task force members chased a tip from someone in Tacoma, Wash., who said that they believed someone named Muhammad had taken target practice with a rifle at a large tree stump. On Wednesday afternoon, F.B.I. agents searched a house in Tacoma where both Mr. Muhammad and Mr. Malvo once lived. They removed a tree stump from the property and searched the backyard for metal casings. An Air Force C-17 was supplied to fly the tree stump out of Washington for testing. Chief Moose and other law enforcement officials said they decided to restrict the release of information about the second letter, as well as Mr. Muhammad's identity, which they established with certainty as early as Monday night.

The Caprice was traced through motor vehicle records to New Jersey. It was co-owned by Nathaniel O. Osbourne, a 26-year-old man who lives in Camden, N.J. Mr. Osbourne was taken into custody today in Michigan after the F.B.I. issued a warrant for his capture as a material witness. As early as Tuesday evening, some police agencies in the District of Columbia area were given a picture of Mr. Muhammad and a description of the Caprice.

On Wednesday evening, at 6 p.m., Chief Moose was scheduled to hold a news conference, where he was planning to reveal Mr. Muhammad's identity to the public, as well as the New Jersey license plate.

But there was a delay of more than six hours. The delay resulted from the wait for an arrest warrant for Mr. Muhammad on firearms violations in Washington State, according to officials.

It may have been a lucky break. If the warrant had come through more quickly, then Mr. Muhammad might have heard the police bulletin and left the area, officials said. Instead, Chief Moose took the microphone at 12:05 a.m. and released the information, though some news organizations had put it out as early as 10 p.m.

Each message by Chief Moose was more conciliatory than the last.

"If you are reluctant to contact us, be assured that we remain ready to talk directly with you," Chief Moose said. "If we can establish communications with you, we can offer other means of addressing what you have asked for. Let's talk directly."

It would end up being Chief Moose's last message, a message that Mr. Muhammad and Mr. Malvo most likely never heard.

Copyright © 2002 The New York Times Company.