Schools under guard as police struggle for clues

Hundreds of extra state and federal investigators fanned out across the Washington suburbs yesterday to try to catch the sniper who has killed six people in the past week and terrorised the area.

Hundreds of extra state and federal investigators fanned out across the Washington suburbs yesterday to try to catch the sniper who has killed six people in the past week and terrorised the area.

The nervousness took hold last week when the gunman, who appears to be an expert shot, killed six people in Montgomery County and the adjoining northern part of Washington DC, and wounded a woman in a shopping centre 50 miles south of the capital.

But the jitters turned to panic when the sniper switched his attention to schools on Monday, shooting and severely wounding a boy aged 13 in Prince George's County, Maryland, to the east of DC, when the youngster arrived at middle school shortly after 8am.

Across the area yesterday, schools were on "code blue lockdown" with virtually all outside activities cancelled. Helicopters patrolled the skies and armed police contingents guarded individual schools.

Some parents volunteered to act as patrol guards at school crossings, but others kept their children away from school altogether.

The precautions spread to the high street, with the Starbucks coffee chain moving tables inside at its shops in the Washington area.

President George Bush described the attacks as "cowardly and senseless acts of violence". A day after emergency surgery at a Washington hospital, the schoolboy victim was said to be in critical but stable condition, and was considered likely to survive.

Any sense of relief was being tempered by the realisation that, if the serial killer remains on the loose, he is likely to strike again.

Indeed many experts believe the sniper is being goaded by the massive media coverage of the crimes. "This is a challenge for him, and he'll be back," Clint van Zandt, a former FBI profiler, said. "We're looking for a needle in a haystack, but this is a killer who enjoys what he's doing. This is emotional heroin for this guy."

The police have received more than 1,200 credible tips, and a $150,000 (£96,000) reward is on offer. But there has been no sign of a breakthrough, despite agents from the FBI and the Bureau of Alcohol, Tobacco and Firearms (ATF) joining local police forces in the hunt. FBI specialists are assembling geographical and psychological profiles of the killer to help to narrow the search. But they warn that the technique cannot be relied upon too heavily and that valid suspects could be eliminated simply because they did not fit the profile.

ATF ballistics experts, although they have established that the same weapon was used in several of the attacks, have not pinned down the precise type of weapon. The gun is believed to be a high-velocity assault or hunting rifle, using .223 calibre ammunition.

There have been no solid sightings of a gunman at any of the attacks. A white van was seen leaving one of the shooting scenes with two people aboard, but searches of such vehicles have yielded nothing.

Police are working on the theory that the killer is male, possibly with a military or police background, but they do not know whether he is acting alone or with an accomplice.

The first killing was on the evening of 2 October. The next morning four people were shot dead within two hours in Montgomery County, a few miles north of the capital.

That evening a man was killed in northern Washington DC. The following afternoon, Friday 4 October, a woman was shot and wounded at a shopping centre near Fredericksburg, Virginia, 50 miles south of Washington.

Each time, the sniper selected his victim from long range, across a large public space such as a highway, car park or shopping centre, and struck with a single shot.