Andy Williams, it seems, was the kind of kid no one took too seriously. Skinny and jug-eared, he was teased by the older teens at Woodglen Vista Park, where he would hang out to ride his skateboard and smoke pot. “We’d tell him to shut up and sit down, and he’d just do it,” says Jessie Cunard, 18, a dropout from Santana himself. “People stole his shoes and skateboard and other stuff, and he just let them.” Raised in small towns in the East, Williams was ill at ease in Santee, Calif., a suburb on the far fringes of San Diego, where he moved with his divorced father last summer. To his friends back in Brunswick, Md., where he lived until 1999, he would complain about the casual brutality of a teenage culture in which any display of vulnerability marked you as a “faggot.” “He got a haircut and they beat him up,” says Mary Neiderlander, whose daughter, Kathleen Seek, had a brief moment of celebrity as Williams’s former girlfriend. But although school officials were still checking their records last week, Williams apparently didn’t impress most adults as the kind of alienated loner who bore watching. “Even the week before the shooting, Andy was a great, loving and fun guy,” says Ashley Petersen, a 14-year-old from the neighborhood. Which is why even the people he’d told about it were shocked on Monday when, according to police, Williams pulled out an eight-shot, .22-caliber handgun and began firing in a boys’ bathroom, killing two students and wounding 13, including two adults.

What is amazing is that, almost two years after the appalling bloodbath of Columbine, no one thought to warn authorities. And it’s not because the school was indifferent to the danger. Congress has all but given up on tougher gun-control laws, so Santana, like many schools, has taken matters into its own hands. Or, rather, put it in the hands of students, who are being asked to bear the brunt of responsibility for their own safety, on the theory that “students are the best metal detectors,” in the words of school-board president Daniel McGeorge. The school offers peer counseling, conflict-resolution classes and seminars in tolerance. Each September, vice principals meet individually with each of the 1,900 students to urge them to come forward–anonymously, if they wish–with information about potential threats from classmates. In retrospect, of course, those in whom Williams confided now wish they’d been a little less sure he was joking. “I kind of feel like I’m to blame for some of this because I could have done something,” says Chris Reynolds, the adult boyfriend of Josh Stevens’s mother, who heard about the plan two days before the shooting. Reynolds said the youth told him he wasn’t serious. Four students who heard Williams talk about shooting up the school, including Stevens and O’Grady, have been suspended for the rest of the school year–for their own safety, school officials say, after threats were made against them.

Obviously, teenage culture has a strong bias against informing. “No one wants the stigma of being a squealer,” says Charles Ewing, the author of “When Children Kill.” (Ewing estimates that 60 to 70 percent of school shooters talked about their killings in advance, and so in theory could have been stopped.) Teens in southern California use “to narc” as a generic synonym for “to inform,” which suggests that they have lost sight of the difference between turning in a friend for smoking pot and alerting authorities that someone is carrying a shotgun. But even adult society has trouble with this concept sometimes. Last week a California legislator proposed a bill to give legal protection to students who report threats. It was prompted by a case in which the parents of a student who was suspended for allegedly making threats sued the child who turned him in. The suit was eventually dismissed, according to news reports, but it cost the second family $40,000 in legal bills.

To break through the stigma, school authorities are rethinking incentives. One way to encourage informing is to pay for it, which is the premise of Crime Stoppers–a program of rewards for tipping off the police that has now spread to an estimated 3,000 schools around the country. In the three years it’s been underway in Tampa, Fla., 48 weapons have been recovered, including eight firearms. Detective Lisa Haber, who runs the program, says the rewards are often not even picked up. What matters is creating a climate in which it’s OK to go to the authorities, especially with the promise of anonymity. “Snitching is becoming cool,” says James Alan Fox, a nationally recognized criminologist. “Ten years ago if you said ‘I’m bringing a gun to school,’ the reaction would have been ‘Yeah, right.’ Now it is taken seriously.” Within days of Williams’s rampage, authorities made eight arrests after receiving tips from students about potential threats at five different schools in southern California. But Santana, still coping with the grief and havoc wreaked by one child’s unfathomable rage, could only wish someone had taken Andy Williams seriously.