An FBI analyst fatally shot outside a Home Depot in Fairfax County on Monday night was definitively identified yesterday as the 11th victim of the roving sniper, who again slipped through a massive dragnet -- but this time was seen by several witnesses.

For the first time since the shootings began two weeks ago, at least one witness, and maybe more, actually saw the sniper aim and open fire on his victim, then leave in a white or cream-colored van, investigators said. In previous shootings, witnesses saw shadowy figures fleeing, but no one saw the actual shooting.

Linda Franklin, 47, of Arlington -- a cancer survivor who was about to become a grandmother -- was shot once as she stood near the open trunk of her car in a covered parking lot outside the home improvement store on Route 50. Her husband, Ted, was standing nearby when the bullet struck her in the head. The couple had been shopping in preparation for a move into a new house.

The shooting, in which the killer changed his tactics and came closer to his victim than in previous attacks, gave investigators their best information yet and even made some guardedly optimistic that as the killer grows more brazen and sloppy, there could be an eventual end to the series of shootings that have sparked fear in the region.

"There was some additional information that we were able to get from [Monday night's] case," said Fairfax County Police Chief J. Thomas Manger. "And I am confident that ultimately that information is going to lead us to an arrest in this case."

Some witnesses caught a glimpse of the sniper, and although some detectives hoped the information would aid the investigation, one source cautioned that "the description is way too premature" to release accurate details or a composite sketch. Similarly, witnesses provided at least partial license plate numbers, although another law enforcement source said the sightings have not yielded a viable lead.

More promising was the presence of the white or cream-colored Chevrolet Astro van with a silver ladder rack on top. It was the second consecutive shooting in which witnesses saw the van. This time, at least one witness said he saw the sniper get out of the vehicle, fire on Franklin, get back in and flee. Other witnesses said the vehicle's rear left taillight was not working.

Police yesterday released two composite images of a van that witnesses say they saw Friday near a Spotsylvania County gas station where a Philadelphia man was fatally shot. Although the images are of different makes -- one an Astro van and the other a Ford Econovan, each with a ladder rack on the roof -- authorities said that only one vehicle was seen and that eyewitnesses gave different accounts of the brand.

Several of the previous shootings had been in more isolated locations, not at a crowded urban crossroads such as the Seven Corners Shopping Center in the Falls Church area, at the intersection of Route 50, Route 7 and Wilson Boulevard. In the earlier attacks, thesniper is believed to have fired from woods or from locations distant enough that no one saw him drive away.

But in this one, sources said, the shooter was much closer. One source estimated the distance at 40 yards. Another source said the fatal shot came from inside the covered parking structure.

"He got up close and personal" this time, enabling the witnesses to see him, one of the sources said.

The shooting Monday night broke an 84-hour lull in the sniper's activities, the longest stretch since the attacks began Oct. 2. Nine people have been killed and two have been seriously wounded while they went about the most prosaic of chores. The shootings have occurred across the region, in Montgomery, Prince George's, Spotsylvania, Prince William and Fairfax counties and in the District.

In Monday's shooting, the overnight ballistics tests confirmed what had seemed apparent from the moment Fairfax County police got the 911 call at 9:19 p.m.: The sniper was back.

Glen Guymon, a Washington lawyer who was shopping at Home Depot at the time, said he talked to a witness who told him that he saw a man shoot Franklin from behind a cream-colored van. Guymon said he and the witness started conversing when police ordered that they remain at the store after the shooting.

The witness, who had already talked to police, told Guymon he was outside the store's main entrance when he saw a man standing next to the van at the end of the aisle where Franklin's car was parked.

The van was not parked in a space but was at a location closer to Route 50, facing west. The witness told Guymon that the man lifted a gun to his shoulder and shot Franklin.

"He said he saw that van parked, a guy standing behind it," Guymon said. "The guy lifted up a rifle to his shoulder and shot the woman, who was standing by her car with her husband. He said the guy at the van got in the van and drove off."

Police were at the scene less than two minutes after the 911 call, dispatch records show, but not soon enough to ensnare the sniperin their dragnet of closed highways, exit ramps and roads.

Several minutes may have passed before the first emergency call was logged -- critical minutes the shooter used to escape.

Police said they moved quickly to shut exit routes from the shopping center but could not provide details about how or when they choked off surrounding roads.

Manger said he did not know how the shooter escaped police as they descended rapidly upon the crime scene. "There are a fair number of ways to leave that area," Manger said. "We had officers in the area as quickly as we could. . . . We were in the area setting up as quickly as we could."

In a now-familiar scene, investigators from local, state and federal law enforcement agencies spread out around the shopping center yesterday, searching for clues as helicopters circled overhead.

About 50 recruits from the Northern Virginia Criminal Justice Academy lined up shoulder-to-shoulder inside the Home Depot parking garage and got on their hands and knees looking for evidence.

Robert F. Horan Jr., the Fairfax commonwealth's attorney, said he believes the killer will be caught -- if he is a single killer. Horan said more than one person may be involved in the shootings.

"I think from the beginning, Montgomery County has been talking about a person or persons, and I think everybody is doing that," he said. "It is possible that you have more than one involved in these behaviors or only one."

The chance that there is more than one shooter has officials reluctantly talking about the possibility of terrorism. Although they say the evidence points away from a terror link, they cannot discount the possibility.

"I don't think we can foreclose that," Homeland Security Director Tom Ridge said of a terrorist link. "Certainly [no one in] the FBI and no one in the White House has foreclosed it."

An official in the administration of Virginia Gov. Mark R. Warner (D) said federal investigators have "not totally discounted" the possibility of terrorism but are skeptical. The shooter's pattern follows that of past serial killers, federal investigators say, and no organized group has claimed responsibility.

"They've looked at that, but they think if it truly was terrorism, the people would be taking a whole lot more credit for it," the official said, adding, "The reason they really don't look in that direction is because this person is becoming bolder and bolder and tends to fit the profile of a serial shooter who ultimately wants to get caught."

The manhunt has government officials taking unusual measures. Maryland Gov. Parris N. Glendening (D) plans to sign an executive order today temporarily banning the outdoor discharge of firearms for recreational purposes in Prince George's, Montgomery, Howard and Anne Arundel counties for the duration of the search for thesniper, according to Glendening spokesman Charles A. Porcari.

Porcari said the order came at the request of law enforcement and political leaders in the four counties, who wanted the ban so that police would receive fewer reports of gunfire that turn out to be false alarms.

"We need to keep focused on whoever's doing the shootings here and not responding to a bunch of shots-fired calls for what were a bunch of hunters," said Montgomery County Executive Douglas M. Duncan (D), who spearheaded the effort.

The order would not prevent gun owners from going to shooting ranges or using their weapons in self-defense. But it would temporarily suspend hunting in the four counties, forcing some of Maryland's 45,700 licensed musketeers, looking forward to the beginning of the three-day muzzleloader deer season tomorrow, to go to other counties or keep their weapons on the gun rack.

Until the killer gets caught, life will not be normal in small and large ways.

Most schools throughout the region remain in a Code Blue lockdown. Motorists think twice before filling their cars with gas.

And a visit to the Home Depot where Franklin was killed is a pilgrimage of grief.

Lidia Salinas and her daughter, Rosa, 12, who live in an apartment complex nearby, stopped at the dollar store yesterday and bought three candles and some white silk flowers to lay at the spot where Franklin died.

As the day wore on, passersby added a potted white mum, a few roses and a bouquet of yellow and red flowers. John Simley, a Home Depot spokesman, placed four orange cones around the shrine.

"At some point, it will just be a parking space again," he said. "But not now."