James E. Swann Jr., the "shotgun stalker" who terrorized two Northwest Washington neighborhoods in 1993, carried out his 14 attacks from Feb. 23 to April 19 of that year before he was arrested by an off-duty police officer who saw his car run red lights. Swann killed four people and wounded five others.
In the case of the Unabomber, Theodore J. Kaczynski, his campaign of attacks spanned 18 years, during which he struck 16 times using mail bombs that killed three people and injured 23 others. The Unabomber manhunt ended in 1996 when Kaczynski's brother, David, sent investigators to his Montana hovel after recognizing his writings in the Unabomber Manifesto jointly published by The Washington Post and the New York Times.
Former FBI profiler Gregg McCrary of Fredericksburg said he believes that the sniper in the recent shootings in Montgomery County, the District and Virginia is a remorseless, egocentric killer whose victims are simply targets "to be acquired."
"These are just victims of opportunity. . . . I think he's probably setting up in an area that he feels it's okay to shoot in, that he can get out of there, and then just waits for a victim of opportunity, someone to come out that he can just put those sights on, and then squeezes a round," said McCrary, who was a profiler from 1985 to 1995 and now runs a consulting business.
"With that, you take away all the other motives, robbery and sex assault and all those other things," McCrary added. "You're down to thrill of the kill, playing god. Having the power over these individuals. Life and death. That's real heady, a real rush. He's on a high now."
Another part of the thrill, he theorized, was that the killer, in most cases, acted in broad daylight in relatively busy locales.
"It's a risky thing. It's a calculated risk, and he's being successful with it," he said.
Another Virginia criminologist and former FBI profiler, Robert K. Ressler, suggested that the killings might be the work of two people. The initial witness report about the white box truck spotted at one of the shooting scenes described two occupants of the vehicle.
Ressler, who now heads Forensic Behavioral Services International, in Spotsylvania, portrayed two people, "one driving, one shooting," both probably white and with previous scrapes with the law.
"They're shocking society," he said. "They're on a roll, having a great time."
D.C. police who investigated the shotgun stalker case said it is virtually impossible to stop a serial shooter by catching him or her in the act.
Although a massive police presence on the street is important to make people feel safe and allow for a quick response to a shooting, they said catching the perpetrator will depend on investigative work and -- as in the Swann case -- considerable luck.
"It's basic investigation. You ask a lot of questions. You think about it. You theorize, and you put it out there," said J.T. McCann, a former D.C. homicide detective and supervisor.
McCann, who now works as a private investigator and has been hired by the family of Chandra Levy to investigate her killing, said police tried to cast as wide a net as possible when searching for the shotgun stalker. They researched sales of shotguns and ammunition in the area, ran down leads of vehicles that fit the one witnesses said was used in some of the attacks, developed a composite sketch of the shooter based on the recollections of a surviving victim and searched for connections among the victims or their locations that might provide a key to why they were targeted.
William O. Ritchie, former head of criminal investigations for the D.C. police, said the killer's apparently excellent marksmanship could lead Montgomery police to contact law enforcement agencies and the military in search of a disgruntled or recently discharged employee.
Staff writers Jo Becker, Phuong Ly and Debbi Wilgoren, research editor Margot Williams and researcher Donald S. Pohlman contributed to this report.