At the scene of the boy's shooting, police stumbled upon a trove of clues. A matted area in the brush opposite the school suggested the sniper had lain in wait for his victim. Police also found a tarot "death" card with the message, "Mister Policeman, I am God." The card, which may turn out to be a prank by someone familiar with the Vietnam War habit of leaving this calling card on the bodies of Viet Cong, was sent to the feds to be analyzed for fingerprints and DNA. The card, it would later be disclosed, also contained a request not to tell the media about its existence. "There is often an indignation on the part of serial killers at news reports about them that are inaccurate, so they start giving little hints about who they really are, what they have done," says Jamie Greene, a clinical and forensic psychologist. "They want recognition."

The indiscriminate shooting of strangers—and a twisted hunt for glory—has plenty of tragic precedent. But generalizations are hard to come by. Killers pick different victims and different M.O.'s, depending on their motivation and mental state. In some cases, the victims fit some sort of pattern. Serial killer Joseph Paul Franklin, convicted of nine murders from 1977 to 1980, has said he was trying to start a race war by shooting African Americans and interracial couples. At the other end of the gory spectrum, notorious shooters like Texas tower sniper Charles Whitman initiate one uninterrupted orgy of violence—as opposed to the methodical drumbeat of the current "hit and run" shootings. Some killers, most famously Son of Sam's David Berkowitz who fatally shot six strangers in New York City, make a point of communicating with the world by sending letters to police and media, which is why some experts began invoking him last week when the Tarot card was discovered.

One of the more instructive analogies, however, may be the case of Thomas Lee Dillon. Convicted of killing five Ohio men between 1989 and 1992, Dillon drove around shooting complete strangers from afar with high-powered rifles. He saw himself an extremely powerful person during these expeditions. And he would later tell forensic psychologist Jeffrey Smalldon that he intentionally picked random victims located across multiple jurisdictions in order to make it harder for police to find him.

Dillon also aspired to commit a crime like none other. "One of his mantras he'd repeat over and over was, ŒThere's never been a crime like this, has there?' There was an extreme pre-occupation with distinguishing himself," Smalldon says. He also had an obsession with control. "Dillon wrote a letter to the local newspaper saying basically, ŒYou can never catch me,' which indicated how very conscious he was of the appeal of operating under the radar, but not too far under the radar; the appeal of having a dialogue with society and basically taunting society." Dillon was captured in part because his best friend reported some of his unsettling comments to the FBI.

In the hunt for the Beltway sniper, one intriguing clue was a spent shell casing found outside the middle school, the only one to be recovered thus far. Like a spent slug, a casing can help narrow down the type of gun that may have been used. So far, ballistics tests have not pinpointed the sniper's weapon. But investigators appear particularly interested in individuals known to possess a Colt AR-15, the civilian version of the M-16 infantry rifle, or a Sturm-Ruger Mini-14 rifle. Both are semi-automatic rifles, popular with target shooters, criminals and some domestic extremist groups.

As the sniper settled into a grisly staccato of killing, he returned to gas stations for his prey and targeted less populated areas, closer to major highways: He killed his ninth victim Wednesday evening while the man was pumping gas at a Sunoco station in Prince William County, Va.. And he killed the tenth victim the next morning, with a state trooper parked just across the way, this time in Fredericksburg, Va., about 50 miles southwest of D.C. On live TV, police blocked off I-95, stopping all northbound white vans in response to a witness report. Geraldo Rivera began broadcasting live on Fox TV, from his cell phone, stuck in traffic with everyone else. But the shooter slipped by once again. So the locals braced themselves for the next live report, making whatever small adjustments they could concoct. Suburban gas station owners began turning their surveillance cameras 180 degrees, so that they pointed away toward the outlying roadways and woods. And a Virginia prosecutor, lacking a suspect, talked to TV cameras about two different ways he could try to impose the death penalty on the sniper, should he ever be caught alive.

—With reporting by Melissa August, Perry Bacon Jr., Eric Roston, Elaine Shannon, Karen Tumulty and Michael Weisskopf/Washington and Amanda Bower and Jodie Morse/New York

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