These bolts from the blue are even more disturbing and disorienting when children are involved. It seems unimaginable that a child could be raped and murdered on her school exchange trip while sleeping in a room with other pupils. Or that a child asleep in a tent in her back garden could be stolen, abused, and killed in the middle of the night.
These events are deeply distressing, and we should be distressed by them. But most of us then go on to worry about the same things happening to us. Are we right? Should we move around in a state of subdued anxiety, a kind of alert fear against the risks that seem to crowd in on us? The real risks, after all, are low: we have about as much chance of being murdered within the week as we have of winning the lottery (ie, very little chance at all). Walking is more dangerous than cycling, which is more dangerous than travelling by car, which is far more dangerous than flying.
Terrible and disturbing though the Dunblane tragedy was, children are still safer in the classroom than in their home. And they are less at risk from strangers than from parents.
The number of child murders has hardly changed in 20 years. Between 1983 and 1993, around 85 children were murdered each year; most of them infants killed at their parents' hands. In the entire decade between 1983 and 1993, only 57 children under 14 were murdered by people they didn't know. It is true that there is a much higher chance your child will be abducted today - but the kidnapper is likely to be your estranged husband or wife.
Such are the facts. But our fears do not reflect them. Parents who cheerfully trotted to school alone a generation ago now escort their own children every inch of the way. In 1971, 80 per cent of seven- and eight-year-olds were going to school alone; today fewer than 10 per cent do. Meanwhile, those few parents who let their kids walk home alone are roundly condemned by neighbours whizzing back in the (lethal) car.
The easiest explanation of this gap between the facts and our fears is the media. When the details of the deaths of Jade Matthews, Sophie Hook and Caroline Dickinson are plastered across the front pages or shouted from the television news, it is hard not to be alarmed. There aren't many front-page headlines about how ordinary life is, and how many children arrived safely at school this morning. Nor are there many mentions in the national press about the countless children killed in road accidents.
But there's a curious puzzle here. Newspapers devote pages and pages to the impact and aftermath of IRA bombs. Yet people still shop in Manchester, still ride double-decker buses round London, and still (in our case) work in Docklands. We know more bombs may go off, but we rarely think about it, and we certainly don't change our lives because of it. London parents don't plan to move to the country just to reduce the risk of their son or daughter being bombed.
Mad cows are another good example. The Government admitted that there might be a link between mad cows and CJD back in March. The newspapers and television news bulletins oozed with anxiety, and gave the issue at least as much coverage as any child murder. For a short time we did stop eating beef. But now, only four months later, beef sales have bounced back up again. We know no more now than we did in March about the extent of the risks to our health, but it seems that most of us are prepared to shrug our shoulders.
The notice we take of the media when assessing the risks around us varies dramatically from one topic to another. With bombs and BSE, it appears that we would rather depend on our own experience than be swayed by news reporting. The idea that the department store we are about to walk into could explode around us is almost inconceivable. So is the notion that the tasty steak in front of us could turn our brains to jelly. But where children are concerned, it seems we can imagine the dangers only too well.
It could simply be that we react more passionately to any suggestion that our children are at risk. Threats we perceive to ourselves as healthy adults from bombs or cows are far easier to deal with and rationalise than threats to our trusting young sons and daughters. Present us with a story about a battered child and rationality deserts us.
Perhaps, too, we have become more sensitive generally to the potential damage to which children are exposed every day. Child abuse was never mentioned 20 years ago, so people didn't fear it. Silence on the subject, however, did not mean child abuse did not exist. Indeed, it was arguably more prevalent than it is today.
Even so, the lurking stranger terrifies us most. Bull-bars on jeeps, malign parents, other children at school: all these are benign compared with the unknown. Maybe it helps to remember, when the headlines are all turning bad, that motor cars kill more than madmen, and that bombs do far less damage than booze.