Sniper investigators said Monday they have been deluged with tips, including false alarms caused by fear and anxiety, as residents of the Washington area remain on edge despite the longest lull in the series of shootings that began nearly two weeks ago.

Cars backfiring, windows shattering and firecrackers popping are among the noises residents have confused with gunshots, believing they are possibly related to the string of random shootings that hit 10 people, killing eight, since Oct. 2.

"We also admit that everyone is edgy. People are hearing things," said Montgomery County police Chief Charles Moose, who is heading the multiagency investigation. "Things are occurring that may normally be overlooked or that may be routine, are certainly getting a higher response from people in their anxiety."

Earlier Monday, for example, four squad cars were sent to a Silver Spring car dealership when the window of a customer's BMW shattered when he slammed the door.

Shooting Tipline
• 1-888-324-9800
• P.O. Box 7875
  Gaithersburg, Md. 20898-7875

For the second weekend in row, the sniper took a break. The sniper's last confirmed shooting death was Friday morning in Spotsylvania County, Va., where a 53-year-old Philadelphia man was gunned down as he filled his gas tank.

The break extended into Monday morning, unlike a week earlier, when a boy was wounded outside a school. The 13-year-old boy remains in critical but stable condition, hospital officials said Monday morning.

Moose, who didn't give a specific number of tips his investigators have received, said people can now write as well as call with their tips. He gave an address -- P.O. Box 7875, Gaithersburg, Md., 20898-7875.

He added that a second composite image -- of a Chevrolet Astro van with a ladder on top seen leaving the scene of Friday's shooting -- was not yet ready. During the weekend, he issued a composite image of a white, box-type truck, based on witness descriptions from more than one shooting location.

Investigators hunting the increasingly brazen killer have logged some consistencies: the killer favors suburban gas stations; fires a single round; aside from weekends, has not let two days pass without opening fire again, and, judging from a tarot card left at one of the shootings, appears to enjoy taunting police.

Authorities have refused to release investigative details, saying they don't want the killer to know what they know.

"We don't want to release anything that may cause ... anyone to think they're a suspect," said Mike Bouchard, an agent of the federal Bureau of Alcohol, Tobacco and Firearms.

Moose had cut back on his news briefings while saying he wished there was more he could reveal.

"I wish we could give you a name, a mug shot and an address but we're not at that point," he said in one of four appearances he made Sunday on national TV talk shows.

The last killing was Friday morning, when a 53-year-old father of six was shot while fueling his sedan in a gas station just south of Fredericksburg, Va. At the time, a state trooper stood just 50 yards away, investigating a traffic accident.

Authorities described the serial sniper as not just a local threat, but an attempt to terrorize already anxious Americans.

"This reminds us that people in our past have tried to intimidate and put fear into Americans," Moose said. "This a strong nation ... and we will not be intimidated."

In Landover, Md., police on horseback and bicycles ringed parking areas before Sunday's Washington Redskins football game against the New Orleans Saints. Fans grilling burgers at tailgate parties said they appreciated being encircled by patrol cars and rifle-toting officers.

"I don't think anybody in their right mind would try something out here," said Bill Freitag of Virginia Beach, Va., a die-hard Redskins fan. "But he's not in his right mind to begin with."

The victims, in Maryland, Virginia and Washington, D.C., were shot as they carried out daily errands. Four were killed at service stations.

Moose and federal officers refused to comment on published reports that the FBI asked the Pentagon to search records for recently discharged soldiers who had undergone sniper training.

Investigators also would not discuss a yellow piece of paper found at Friday's killing site, which reportedly contained scribbled directions from northern Maryland to the Capital Beltway.

A white truck matching composite images compiled by the FBI was still being sought. And as Sunday wore on without another shooting, a reporter asked Moose if he dreaded Monday morning.

"We won't make any assumptions about any kind of pattern," Moose said. "I never approach Monday morning with a sense of dread."