Falls Church, Va. ? A woman was shot dead Monday night outside a Home Depot store, and police were trying to determine whether the slaying was related to the sniper spree blamed for eight killings in the region in the past 12 days.

Police swiftly closed highways in the area, about 10 miles west of the nation’s capital, and said they were on the lookout for a white van from which the shooter might have fired. Witnesses at some of the earlier shootings also reported seeing a white van or truck.

The woman was felled by a single shot about 8:15 p.m. CDT, authorities said. All the other deaths in the spree were also caused by one shot, and two people also were wounded by a single bullet.

Members of a Maryland task force investigating the sniper attacks were working with Fairfax County authorities to see if Monday’s victim was the sniper’s ninth.

“It’s too early to tell (if the shooting is linked), but we are working it and investigating it with that potential in mind,” Fairfax County Police Chief Tom Manger said at a news briefing.

He said there were several witnesses.

Virginia State Police said they were on the lookout for a cream-colored Chevrolet Astro van with the right rear taillight out, last seen traveling east on Route 50 from Falls Church. Interstates 66 and 95 are nearby.

The Home Depot is in the Seven Corners Shopping Center, a 450,000-square-foot strip shopping center with a parking garage. The victim’s body lay under a sheet 30 yards from the store entrance, in the parking lot in front of the store.

The woman was shot in the head as she and her husband loaded packages into their car’s trunk, said Ellen Qualls, a spokeswoman for Virginia Gov. Mark R. Warner. Someone fired the fatal shot from a van, she said.

Kristin Reed, a supervisor at the Barnes & Noble bookstore in the sprawling strip mall, said six employees were locked inside the store with an FBI agent.

“Cops and cops and more cops,” Reed said of the scene outside. Shopper Raymond Massas said he “heard one shot. Not very loud, like a snap. After that I heard people start panicking.”

Two police helicopters circled the scene as bystanders looked on.

“It hasn’t been this frightening since 9-11,” said Bob Bakley as he stared across Route 50.

Added Abdel Elkheshisn: “We thought, ‘It’s in Maryland. It’s not here, it’s far away.'”

The sniper had shot 10 people in the killing spree that began Oct. 2. Friday morning, a 53-year-old Philadelphia man was gunned down in Spotsylvania County, Va., as he pumped gas. The killer had gone two straight weekends without an attack.

Earlier Monday, the longest lull yet in the Washington sniper’s killing spree brought little relief as jittery residents flooded police with calls upon hearing car backfire, firecrackers or breaking glass.

“Everyone is edgy,” said Montgomery County Police Chief Charles Moose, who is heading the investigation. “People are hearing things that may normally be overlooked.”

President Bush said the “cold-blooded” attacks have made him sick to his stomach. “I weep for those who have lost their loved ones,” he said. “The idea of moms taking their kids to school and sheltering them from a potential sniper attack is not the America that I know.”