It's the keenest challenge for law enforcement: how to find a killer or killers who are randomly targeting victims from shopping centers to gas stations to middle schools with no apparent motive to link the crimes.
The intent, at least on the surface, appears to be to instill terror. With the shooting of a 13-year-old boy outside a Maryland middle school Monday morning, the eighth apparent victim in six days, the gunman or gunmen is succeeding on that front.
Thousands of parents pulled their kids out of schools, as extracurricular and outside activities were canceled. Usually busy shopping malls, gas stations, and neighborhood streets were quiet. Police throughout the Washington metropolitan area were on heightened alert, guarding morning commuters from rooftops and squad cars.
Speculation on a motive of the skilled marksman or men is also running rampant from a generalized hatred of humanity to a delusional sense of omnipotence to links to the Al Qaeda network. Or maybe even killings as a twisted form of sport.
Whatever the motive, the key, say criminologists, is for the public not to give in to the fear and for the media not to inadvertently glorify the shooter or shooters. "It's really critical that the media coverage focuses on the killings and not the killer, that they shed light on the crimes without putting a spotlight on the perpetrators," says James Fox, a criminologist at Northeastern University in Boston. "You don't want to intensify their feelings of importance and invincibility. It's a fine line."
As of Monday morning, police had not definitively tied Monday's school shooting to the other attacks. While the random nature has many of the hallmarks of the earlier incidents, it could be a copycat or unrelated event.
Still, it's occurring in the current atmosphere of intensified fear. "We all live around there," says Mark Jones, a resident who was walking near Benjamin Tasker Middle School in Bowie, Md. "It could have been me or my neighbor. I didn't know what was going on."
School security was stepped up throughout the Washington metropolitan region. Prince George's County put all schools on a "code blue" lockdown status, as police swarmed the middle school crime scene and crisis intervention counselors arrived to begin aiding students and parents.
In neighboring Montgomery County, Md., "code blue" was also adopted as a precaution, with outdoor recess and field trips canceled, and tightly restricted access to and movement inside the schools. Washington, D.C., schools curbed outdoor activities as well.
"We'll still make sure kids get their bathroom breaks and get lunch," says Brian Porter of Montgomery County schools. "But we keep them away from the windows."
For older students, Mr. Porter says, the tragic incident, as negative as it is, offers an opportunity for learning. "These are lessons to be learned: Life is not always easy," he says. "[This is] a profound opportunity for in-depth discussion on current events."
FOR police, the next few days will be critical in trying to resolve the case. "If he keeps shooting, they will solve it," says Richard Rosetti of Safir Rosetti, a security consulting firm in Washington. "If he stops shooting, it will take a long time."
Police have been collecting the scant evidence, like the reports of the white cargo truck fleeing one of the scenes, along with hundreds of tips. They've used computer-generated analysis to try to establish a profile of the killer or killers.
But for all the cutting-edge technology, much of the police work required is basic shoe leather. "Really, it's 19th-century police work, trying to figure out the reason if any people could be involved," says David Kennedy, a criminologist at Harvard University's Kennedy School of Government. "It's an enormous task, that requires vast quantities of personnel time."
As laborious as it is, the more information that can be gathered, the more success police will likely have. "If you have a profile, you can begin looking for people who fit in that geographic profile where the person feels comfortable," says Charles Bahn, a forensic psychologist at John Jay College in New York.
Residents of suburban Maryland are trying to go on with their daily lives in newly transformed neighborhoods. Over the weekend, spouses talked to each other about whether it was "safe" to travel on certain streets. The simple act of eating outdoors has become an act of defiance, and it is not uncommon here to see white "box trucks" pulled over by police. Even though the killer has probably long since ditched the truck, police believe it may contain key forensic evidence.
At a Shell station in suburban Maryland where a woman was shot Thursday, the four pumps are still wrapped in yellow police tape. Business is quiet, too, at a gas station nearby. "It's been really slow," says cashier Janet Martinez. "The whole weekend was slow."
Ms. Martinez says even her drive to work has made her edgy. "It's scary, you know. I have two kids, and now I'm worried about just getting on the road," she says.
At a Getty station, a TV monitor shows the latest news of the school shooting in Bowie, where the 13-year-old was wounded and is in stable condition. Children are being led away by parents. "I just got off work," says Marvin Baffour, a chauffeur. "I started at four o'clock and I'm going home now. I'm telling my boss, no more four o'clock starts."
Ron Scherer, Faye Bowers, and Dante Chinni contributed to this story.