The boy was the son of an official at the World Bank and, by all accounts, a model child. His parents were away in Europe and he was at home because he had sacrificed his holidays to take up a summer fellowship at the Washington Children's Hospital. Hours before being killed he had delivered a speech to fellow students to mark the end of the fellowship programme.
As they related the tragedy, our neighbours showed obvious shock and outrage. Although the black assailant later gave himself up to a local psychiatric hospital and is now in custody, they find themselves facing the same reality that most Americans face all the time: that in this country, saturated by guns and filled with racial hatred, the danger of mortal attack always lurks.
For the residents of Chevy Chase Park, on the far north- west fringe of the capital, murder had for a long time been something that happened elsewhere. This is a neighbourhood of quintessential suburban cosiness and privilege. Brick or clapboard houses line quiet streets which to a British eye could almost as easily be set in a leafy outcrop of London, perhaps Twickenham, as in America. As far as anyone can remember, there has not been a killing in the immediate area for more than 10 years. And in most minds, murders are committed by blacks against blacks - not against teenage whites of well- to-do families.
We too, as recent arrivals in the area - and in the US - had been virtually taken in by this now-broken sense of immunity to the violence of the rest of the city. It seemed possible, for better or worse, to live here and be barely conscious of the strife and misery of people just two, three miles away. At nights, we hear sirens wailing in distant, poorer neighbourhoods, but they rarely pass our way. On fine days, young children play unaccompanied by adults in front gardens and on the pavements. At weekends, some will set up little roadside stalls to sell lemonade or cobs of corn.
And all this in Washington, which has the worst per capita murder rate of all US cities - a fact that seemed particularly to concern friends and family in England at the time of our moving here. Even with its relatively small population, the capital averages more than a murder a day, with a grim total in 1991 of 485. In a normal year, one in every 440 black teenagers in Washington will be slain. The disgraced former mayor, Marion Barry, barely improved the image of the city in 1989 when he commented rather unfortunately: 'Outside of the killings, we have one of the lowest crime rates in the country.'
Since the murder last Friday of young Alain Colaco, the barrier between those statistics and the daily life of the residents of Chevy Chase has been breached. Our neighbours have told their two boys, who are 13 and 10 years old, to stay out of their front garden where most evenings they have played catch, regularly losing balls in our scrawny rhododendron bushes. Now they will have to make do with the much smaller backyard. Even that has a small alley behind it and so can never really be safe.
The residents on our street are barely reassured that the killing appears to have been totally random. The murderer had walked three miles from his home in north-east Washington, largely through uninhabited parkland, with his gun under his shirt. He did not know the victim and, in police interviews, his only explanation for killing him was that 'he had the urge to do it'. Such mindless killing, though, is as much a part of the daily slaughter going on all across America as the more common drugs and gangland slayings.
The sadness of the loss of this one boy was underscored by the apparent brightness of the future that lay before him. He planned to be a scientist and was down to enter trials for the next US Olympics soccer team. In his speech to his student friends, delivered hours before his death, he commented on the value of his experience at the children's hospital. 'It has provided me with opportunities I would not have had otherwise, such as the opportunity to sit and talk to patients,' he said. 'These are things that will help me no matter what I do in life.'