There has been a rush to locate them. Moralists have seized eagerly upon screen violence and the impoverished male self-image which takes such comfort in fantasising about sex. Others have spoken portentously about the world wide web, which is sticky with vapid banalities about devil worship and Hitler. There is a miasma here, of course, but we should not mistake effect for cause, for all of the above are symptoms of an immense cultural poverty rather than the conditions which bring about moral decay.
America is a continent of extremes, but it is significant that tragedies such as that of Columbine High do not occur at the extremities but in the suburbs. The high school is located in Littleton and its tragedy is that of every little town. If, like everything else, it is writ larger in the United States, that it not to say the problem does not exist in its own way in our own small communities. It is hard to pin down but it is something to do with the increasing solipsism of the world in which our teenagers live. It is not simply that they retreat into bedrooms which seem as self-contained as an astronaut's capsule, each with its own TV, stereo-system and wired-up computer. It is that they retreat into a world view which - now that a combination of compulsory education and consumerist aspiration have extended the teenage state from the age of eight to the early 20s - becomes increasingly self-referential and self-validating.
The things which once linked teenagers to the value systems of the rest of society - from apprenticeships in the world of work, through youth wings of adult organisations like tennis clubs or churches, to limitations on travel which meant that youths and their fathers drank in different rooms in the same pubs - all these are long gone. And with them have vanished the frameworks of reality which placed social restraints on the individual's freedom to think, say, do, or buy whatever is desired. Gone, too, are the touchstones which helped with the ability to distinguish between adolescent fantasies - whether of ambition or revenge - and actions which are allowable in real life. Most healthy teenagers discover new mechanisms to compensate and help them make sense of the fragmented world in which they today find themselves. Some, like the killers Eric Harris and Dylan Klebold, evidently do not. They have lost the external measures of when the fantasy game is over, or ought to be, and they have no inner mental thermostat to tell them when the lurid fantasies of violence, satanism or Hitlerian hero- worship must be allowed to slip away. In that sense the laughing killers are the victims of a degraded society in which evil arrives not starkly but though a creeping corruption.
There is nothing uniquely American about this. Perhaps in Britain there is a little more solidarity among our young people in the manner and expression of their adolescent rebellion. Perhaps our schools do not polarise into the successful and failures, the beautiful and the losers, the jocks and the geeks, with the kind of extremity evident in Columbine High. But if teenage estrangement is not so dramatic here, it may be no less pernicious. It is a phenomenon which, as we tut and shake our heads at the events in Colorado, we would be wise not to ignore.