WASHINGTON, Oct 8: Children returned to school in the Washington suburbs under heavy police guard on Tuesday, a day after a 13-year-old boy became the latest victim of a sniper who has killed six people.

Schools in the counties where the sniper has struck kept children indoors and police helicopters buzzed overhead as public anxiety mounted over the eight random attacks in days.

As an official reward for information on the killer grew to 160,000 dollars with public donations, police insisted they were doing everything in their power to catch the perpetrator.

“We’re going to continue to do the work that is necessary,” Montgomery County, Maryland police chief Charles Moose told reporters in Rockville, Maryland.

As police built up a psychological profile of the likely killer, Moose urged residents to report any strange behavior or anyone “bragging about some situation that sounds terrible”.

The boy shot on Monday as he was being dropped off at school in Prince George’s County, northeast of Washington remained in critical condition in hospital.

The boy was wounded in the spleen, stomach and lung by a single bullet and underwent several hours of emergency surgery at the Children’s Hospital in Washington.

Five people were shot to death within a 16-hour period on Wednesday and Thursday in Montgomery County, an affluent suburb north of the US capital.

A sixth victim was shot in the chest late Thursday while standing on a street corner close to the Maryland border in Washington.

And on Friday, a woman was shot in the back in the parking lot of a shopping mall in Fredericksburg, Virginia, some 80 kilometers (50 miles) south of Washington. She was hospitalized and reported in fair condition.

No clear pattern has emerged in the attacks: The victims were of both sexes and of varying races and ages.

But ballistics tests have linked six of the eight shootings. Two bullets were in poor shape, making it difficult to link them conclusively to the other shootings, officials said.—AFP