A woman was shot dead last night outside a Home Depot store in Fairfax County in an attack that appeared similar to a series of snipershootings that have killed eight people and spread fear across the Washington region for nearly two weeks.

The shooting in the Falls Church area occurred about 9:15 p.m. at the Seven Corners Shopping Center, which is bounded by major Northern Virginia traffic arteries, and it prompted police to set up checkpoints on principal roads for miles around. Traffic came to a standstill.

The attack occurred on a day when President Bush spoke about the series of killings, which have curbed school activities, raised apprehension across the area and prompted many people to rethink daily routines.

Last night's killing, about six miles from the District, occurred much closer to the core of the metropolitan area than three shootings last week that took place in less densely populated Bowie, Spotsylvania County and Prince William County. The previous week, five people were slain in Montgomery County and one in Northwest Washington, and a woman was wounded in Spotsylvania.

Last night, Raymond Massis, 42, of Falls Church said he was at his car in the parking lot when he heard a loud crack.

"It sounded like a shotgun. I've worked security; I know what guns sound like. It wasn't a pistol; it was a big gun," Massis said.

A salesman at the Home Depot said his store went into lockdown mode.

"People were crying. Everyone was crying," said the salesman, who was reached by telephone.

A teenager looking out from his apartment heard a noise like a loud bang and ducked at the sound.

"As soon as I heard it, I knew what had happened. I knew somebody was shot. I knew it all day that something was going to happen," said Rodolfo Zeba, 13.

Rodolfo said he turned off his bedroom lights and crawled into his younger sister's bedroom to tell her to stay put.

Last night's attack apparently involved a single shot, as did the shootings that authorities have linked through ballistic evidence to the sniper.

Police broadcast a lookout for a light-colored van seen leaving the area. Witnesses at the scene of a sniper shooting last week in Virginia described a similar vehicle. Early reports gave varying descriptions of the van: a white 1990 Dodge, a cream-colored GMC van and a white Chevrolet Astro van.

A Virginia State Police spokesman said the latest lookout was for a cream-colored Chevrolet Astro van with a silver ladder roof rack and its left taillight out.

The victim had just left the home improvement store with her bags and was at her car when she was shot, said Fairfax County Police Chief J. Thomas Manger. Ellen Qualls, press secretary for Virginia Gov. Mark R. Warner, said Fairfax police reported that the woman's husband was with her at the time of the shooting.

Speaking about 11:25 p.m. in an impromptu news conference at the shopping center, Manger said "it is too early to tell" whether last night's shooting could be linked to the earlier attacks. Nonetheless, he said, "we are investigating with that potential in mind."

Officials closed most of the bridges between Virginia and the surrounding jurisdictions of Maryland and the District, said Joan Morris, a Virginia Department of Transportation spokeswoman.

Police checkpoints funneled traffic on Interstate 395 southbound at Edsall Road, and officers shut the outer loop of the Capital Beltway over the Woodrow Wilson Bridge into Maryland.

Patrol cars searched car by car at the American Legion Bridge, and a checkpoint was set up on westbound I-66 at Nutley Street in Vienna.

Qualls said police used the same "swarming strategy" to stop traffic that had been used last week after the shooting in Spotsylvania.

In that incident, police appeared almost everywhere, blocking exit and access ramps up and down I-95 between Alexandria and Fredericksburg, assault rifles slung over shoulders. They peered down from overpasses, radios in hand.

Immediately after being notified last night, said state police spokeswoman Lucy Caldwell, state troopers and officers in local jurisdictions shut down every road in the area.

She said that the roads closed included I-66 and I-95 and George Washington Memorial Parkway. Caldwell said cars were checked and were allowed to pass single file only after close scrutiny.

The closing lasted for about three hours. I-66 was backed up for more than 10 miles, Caldwell said. She said that for a long period, nothing moved on I-395.

"The entire Virginia corridor was closed," she said.

In what may have been an eerie coincidence, two of the previous shootings connected to the sniper occurred near Michaels craft stores. (In the first shooting, no one was hit, but a bullet hole was left in the store window in Aspen Hill.) There is a Michaels store at the shopping center where last night's attack occurred.

Last night's shooting occurred nearly 84 hours after the last attack that was conclusively linked to the sniper. It followed a weekend free of such shootings.

It occurred near the end of a day that was a holiday for many area residents, in an area in which stores and apartment houses are relatively close together. In the first minutes after the attack, many people reported hearing or seeing something.

Qualls, Warner's press secretary, said there were early reports from the scene indicating that the assailant may have fired "either in or near a van." She said that according to one report, the attacker stepped from a vehicle, put a rifle to his shoulder and fired.

Platoons of law enforcement officers, part of one the the biggest manhunts in the history of the region, converged on the area. Witnesses counted at least 50.

The beam of a high-intensity searchlight, mounted on a hovering helicopter, swept the area in a constant circle. Officers cordoned off the Home Depot parking lot with yellow crime-scene tape. A single ambulance was parked at an angle in the parking garage, blocking from view whatever had taken place there.

Police also prevented cars from entering or leaving most of the lot, which is at the east end of the shopping mall. Drivers waiting to exit were allowed out one car at a time.

Traffic quickly backed up both directions on Route 50 as police shut that road, then allowed cars to proceed one at a time as they checked vehicles.

The shooting had an immediate impact on activities planned for today.

Daniel A. Domenech, Fairfax County school superintendent, said: "Right now we're planning on opening school at the regular time, but we have been under extreme security measures, and those procedures will be in place tomorrow. All of our students will be kept indoors . . . and certainly in the immediate vicinity of the Seven Corners area, they will be under greater protection than is usual."

At the White House yesterday, President Bush called the sniper "a sick mind who obviously loves terrorizing society," and he promised to continue "lending all the resources of the federal government" to the investigation of the shootings.

"I'm just sickened, sick to my stomach, to think that there is a coldblooded killer at home taking innocent life," Bush said in his strongest statement yet on the attacks that have killed eight people and wounded two since Oct. 2.

Members of the task force hunting for the sniper responded yesterday to a report of a Baltimore man driving a white van similar to one seen leaving the scene of the shooting last week in Spotsylvania County. The man was questioned in Baltimore and discounted as a suspect.

"It's not related," said Capt. Nancy Demme of the Montgomery County police. "We can't explain any further."

The investigative task force quickly dispatched a team to Baltimore after it was reported that local police had found a rifle that used the same .223-caliber ammunition fired by the sniper in a van driven by the Baltimore man, whose identity was withheld by police last night.

The weapon was rushed to a federal ballistics laboratory for testing, and police sources said they determined that the gun did not match the one used in the shootings.

A law enforcement source said, "We have three or four of these [fruitless tips] a day." The only difference yesterday was "you found out about this one."

"This is what the police do. They follow up leads like this, and many of them sound promising," the source said. "When they say they're making progress, they mean that they're following leads like this every day."

Investigators have questioned dozens of people who ultimately were eliminated as suspects, the source said.

About half a dozen men were considered for a time the "most promising" sniper suspects, but none of the leads turned out, the source said.

Responding to reporters' questions at the White House yesterday, Bush said of the sniper attacks and the fear they have caused: "I weep for those who lost their loved ones. . . . The idea of moms taking their kids to school and sheltering them from a potentialsniper attack is not the America I know."

The president said he has been updated daily on the investigation -- including "a full briefing" yesterday by FBI Director Robert S. Mueller III -- and said authorities have found no indication that the shootings are linked to a foreign terrorist group.

"First of all, it is a form of terrorism, but in terms of the terrorism we think of, we have no evidence," Bush said. "But anytime anybody is randomly shooting, randomly killing, randomly taking life, it's coldblooded murder. . . . And we're doing everything we can to capture whoever that might be and bring them to justice."

FBI Special Agent Gary Bald said yesterday that the full weight of federal investigative ability has been employed in the case and that he saw no reason for his agency to take command of the effort.

"There hasn't been any talk among the investigative team of the FBI taking this case over," Bald said. "There are no resources that we have that are at our disposal that we aren't bringing to bear. . . . The group is working very effectively together."

After three days without a reported sniper shooting -- the longest quiet stretch since the attacks began Oct. 2 -- Montgomery County Police Chief Charles A. Moose said yesterday that authorities "are indeed making progress" in the case.

When asked why police would not release a psychological profile, which the FBI has been working on, Moose said: "None of that has been released because, again, we do not want to paint a picture that somehow causes people to exclude the possible suspect or people involved in this."