And so it begins all over again: the schoolgirls hugging with anguish, the bodies sprawled over suburban lawn, the grieving mothers, the grainy newspaper photo of a kid who looks too young, too clean-cut to be the mass murderer next door. Above all, there comes the restless search for answers: Why? Where next? How do we stop it?

Teach our children to respect life, says President Bush. Who could disagree? But what exactly has to change in our culture of parenting to convey that message effectively? Divorce is one possibility. Research shows strong links between divorce and both youth suicide and youth crime. The killers' parents lived on two different coasts -- his mom and brother in Maryland, he and his dad in California. Surely Mom and Dad must be wondering now if they had only stayed together, worked together, maybe one of them might have noticed and averted this horrible tragedy, this heinous crime?

But whatever the limitations in the values of his parents, certainly they did not encourage their son to become a cold-blooded killer. Did they fail to remind him: "Honey, don't mow down your classmates, it's not nice"? Just say no to murder? Surely that is not what's missing in our children's values education.

So what is it? Where are we going wrong that we are raising up such killers among us?

I found a clue in the comments of a 15-year-old Santee girl who is a friend of the killer -- comments even more horrifying to me than the acts themselves.

"He's still my friend," Vanessa Willis told the Los Angeles Times. "I'm not going to dislike him just because he killed people. He's not sick in the head like those people from Columbine. He's a nice guy."

Very astute listeners, when they get over the shock, may hear in this nice young suburban girl's words the new emerging model of morality, the same model of morality that President Clinton relied on to get through his little troubles in office. Sure, what he did may have (hurt his wife)/(killed two schoolmates), but what did he ever do to me?

Beginning in the sexual realm, where this new moral model is now the dominant way of reasoning (what's right and wrong depends on the person's values. Being a virgin or a slut are equally cool, as long as it's your own choice), it appears now to be migrating, as ideas do. Most teens, or professors for that matter, do not take their moral logic so far, of course.

But we should recognize this new model is not some aberration, not a form of psychopathology. It is cross-culturally a very common way for humans to approach morality, a.k.a. "tribalism." Those who belong to my clan, I'm obliged to treat well. Those who are outside my clan are outside my moral concern. It is such moral tribalism that leads these school killers to warn friends to stay away (killing a friend would be wrong).

Morality is personal. What's right for you isn't necessarily right for me. And who you wrong doesn't matter to me, as long it's not me: "I'm not going to dislike him just because he killed people."

The old moral model that dominated Western civilization was based on the opposite premise: Moral rules are the same for everybody, everywhere. Kant called it the universal imperative. More recently it's been dubbed "objective morality." Belief in an absolute moral code transcending personal tastes and affections is not an inevitability. It is the product of two millennia of thinking and teaching about God, reason and human nature. And it can disappear, it seems, virtually overnight.