B By Stephen Braun, Jonathan Peterson and Lisa Getter

OWIE, Md. – The sniper taking deadly aim in Washington’s suburbs struck again Monday, critically wounding a 13-year-old boy as he stood outside the doors of his middle school – the eighth victim in a series of shootings that began last week.

Forensic evidence linked Monday’s attack to the earlier shootings, which left six people dead and one wounded, police said. The latest incident prompted officials to intensify their investigation and bolster security for thousands of anxious students and families from Baltimore to Virginia.

The gathering horror already set off last week mounted again Monday with new urgency over a long, strained day that indicated that even the region’s children were at risk.

In suburban Maryland, where most of the shootings have occurred, frightened parents rushed to their children’s schools, police teams stood vigil in schoolyards and public officials urged residents to patrol their own street corners.

“All of our victims have been defenseless, but now we’re stepping over the line. Our children don’t deserve this. I guess it’s getting to be really, really personal now,” said Montgomery County Police Chief Charles Moose, whose eyes moistened with tears as he spoke angrily.

On Monday evening, Moose announced that at his request the federal government had created a multi-agency task force, which will work under his direction with authorities in the areas where the shootings occurred. It will include elements from the FBI, the Bureau of Alcohol, Tobacco and Firearms, the U.S. Attorney’s office in Baltimore and other agencies.

Moose’s detectives in Montgomery County were confronted Wednesday and Thursday with five killings in less than 16 hours–victims shot as they performed the mundane tasks of everyday life such as shopping and pumping gas.

Three of those fatal shootings and a similar one late Thursday just inside the District of Columbia–as well as the wounding of a woman some 50 miles away in Virginia on Friday–were linked to the same variety of high-velocity .223-caliber bullet found Monday inside the chest and abdomen of the eighth-grade Bowie middle school student. The bullets in two of the killings were too badly mangled to provide any forensic evidence, officials said.

On Monday night, police officials in Prince George’s County, where the school shooting occurred, and federal firearms investigators said that ballistics tests performed on a fragment removed from the wounded teen-ager confirmed the link with the other cases.

“Based on circumstances and our tests, the projectile is identical to those recovered at the other crime scenes,” said Joseph M. Riehl, assistant special agent with the Baltimore office of the federal Bureau of Alcohol, Tobacco and Firearms.

The eighth-grader was in critical but stable condition at Children’s Hospital in Washington, where he underwent nearly three hours of surgery. Dr. Martin Eichelberger, the trauma surgeon who performed the operation, said the bullet shattered inside the boy’s chest, piercing his stomach, pancreas, spleen, diaphragm and one lung.

Surgeons gave a bullet fragment to a Prince George’s detective, who then turned it over to ATF agents for ballistic tests.

Vowing to apprehend the rifle-wielding “bad guy,” Prince George’s County Police Chief Gerald Wilson confirmed that police were looking for a white “box truck,” the vehicle already being sought by Montgomery County police in connection with at least one of last week’s slayings.

William Aleshire, a Bowie city councilman and retired D.C. Metropolitan policeman, said the truck may have been carrying temporary Virginia registration tags–a report that police officials declined to verify.

Federal and local police officials moved Monday night to consolidate their detective work into the shootings.

It was unclear whether the consolidated effort would lead to federal charges if a suspect is apprehended. But even before the latest shooting, federal authorities had dramatically escalated their involvement in the investigation over the weekend.

The FBI, meanwhile, was preparing a psychological profile of the shooter, to determine the person’s background, possible motivation and pattern of shooting. The FBI also deployed agents to a command post in Montgomery County, while ATF agents performed ballistics tests and Secret Service agents and U.S. marshals assisted in the investigation and school security.

The FBI’s high-tech “Rapid Start” computer program was being used to track and correlate thousands of leads. “They’re coming in from all over,” said one official. Moose added that more than 1,000 “credible leads” were being checked.

In Washington, President Bush also pledged federal aid and said the nation has “witnessed a series of cowardly and senseless acts of violence in the greater Washington area.” A $50,000 reward posted for help in cracking the case was boosted to $160,000 by dusk Monday.

As police learned the sketchy details of the shooting at Tasker Middle School in the predominantly middle-class black community of Bowie, school officials in the region moved swiftly to provide security to students and reassure parents.

Classes were locked down in Montgomery and Prince George’s counties, preventing any visitors from entering. Outdoor activities were canceled as far north as Baltimore and south into Virginia’s Spotsylvania County, where the shooting Friday had occurred. And Montgomery and Prince George’s school officials beefed up security, bringing in police and, in some cases, even using Secret Service and Maryland State Police officers to patrol school grounds.

At nightfall, Montgomery County Executive Douglas Duncan urged parents to act as “safety patrols” outside schools and at bus stops to protect their own families.

Detectives continued interviewing some teachers at Tasker late into the day.

Outside, other detectives aided by gunpowder-sensitive search dogs combed a wooded area several hundred yards away and across the street from the school–a considerable distance from where the single shot was apparently fired.

Just dropped off by his aunt a half-hour before the start of school, the critically wounded boy crumpled to the ground just yards from the school door, crying out after he was struck, police said. Officials said that the boy’s aunt, a registered nurse, rushed to his side and helped him into her car, then drove him to a nearby hospital. But later in the day, several Tasker instructors said that a seventh-grade teacher was the first to reach the victim.

The wounded boy “actually stood up” and “tried to get into the car himself,” said Prince George’s County Councilwoman Audrey Scott. “He was conscious the whole time.”

Inside, students were kept in their classrooms, uncertain what was going on outside. “They really didn’t know what happened,” said Damaris Ramos, 13, an eighth-grader. “Some people were crying because they thought (the sniper) was going to come into the school.”