BOWIE, Md. — A 13-year-old boy was shot and critically wounded as his aunt dropped him off at school Monday, bringing fresh terror to the Washington area where a sniper killed six people last week. Another shooting Monday in the District of Columbia also was being investigated.

Anxious parents streamed in to retrieve their children from the school, and police in neighboring Montgomery County hunting for the serial sniper rushed to the scene. Officials stressed that no link to the Montgomery shootings had been established, but many school districts in the area canceled outdoor activities.

Montgomery County Police Chief Charles Moose said a man sitting in a vehicle in Washington had also been shot, but the case’s relationship to the others was unknown.

“It is very recent, very hot,” he said at mid-afternoon, explaining he had few details. He said he thought the man was wounded and not killed.

The location of that shooting in Washington is near the line with Prince George’s County, the suburban county where the boy was shot shortly after 8 a.m. outside Benjamin Tasker Middle School in Bowie.

“Whether they’re connected or not, the fear has ratcheted up quite a bit,” Montgomery County Executive Doug Duncan said.Sharon Healy had just sent her 12-year-old son, Brandon, to school on his bicycle when she heard of the shooting. She said she ran to the school and pulled him out of class.

“You think you’re safe, but you’re only as safe as your next step,” Healy said. Said her son: “I was scared.”

The boy was shot once, in the chest, and was in critical but stable condition and breathing on a ventilator following surgery, said Dr. Martin Eichelberger of Children’s Hospital.

Eichelberger said he was optimistic about the child’s chances for survival, though the boy has a “significant injury” to a lung.

The doctor also said the surgery team made a special effort to find a portion of the bullet, which they gave to police.

The shooting happened well before classes were scheduled to begin, so there were not a lot of witnesses, Prince George’s County Police Chief Gerald Wilson said. A gunshot was heard, and the boy slumped over and told his aunt he thought he had been shot, Wilson said.

His aunt took him to a small hospital in this suburb northeast of Washington, and then he was transferred by helicopter to Children’s Hospital.

Police cars surrounded the school and officers put up crime scene tape and searched the campus.

Othar Haskins, 13, standing outside the school with his mother, said he was a friend of the wounded boy.

“He’s funny, he’s always around friends,” Othar said. “He helps you out when you need it. He’s a good friend.” Othar cried and put his head on his mother’s shoulder as he spoke.

On Wednesday and Thursday, five people were shot to death by a sniper in a 16-hour span in Montgomery County. A sixth victim was killed Thursday in Washington, D.C. On Friday, a woman was shot and wounded in Virginia.

“All of our victims have been innocent and defenseless, but now we’re stepping over the line,” Moose said. “Shooting a kid — it’s getting to be really, really personal now.” At one point, tears streamed down his face.

But he stressed that it was too early to know whether the shooting of the boy was related to the sniper slayings.

White House press secretary Ari Fleischer said federal authorities — the attorney general, Treasury Department and Bureau of Alcohol, Tobacco and Firearms — have been “very involved on the ground and have lent support and equipment.”

Asked if there was any evidence of terrorism, Fleischer replied: “I’ve not heard anything like that, but the fact of the matter is that people are trying to determine who the shooter is, or shooters are, and we continue to help local officials in that endeavor.”