The woman was shot in the back in broad daylight outside a Michaels store on the outskirts of Fredericksburg, Va. Police said she was loading packages in her van when an unknown assailant shot her.
Friday evening, a spokesman for Fairfax Hospital in northern Virginia said the woman was being treated in the emergency room but declined to list her condition.
On Thursday evening, a 72-year-old man was shot and killed as he was standing on a corner in northwest Washington. Police said the man, Pascal Charlot, was shot in the chest.
Police and agents from the Federal Bureau of Alcohol, Tobacco and Firearms were testing fragments of the bullet used in the Washington shooting to see if it matched those recovered in the shootings Wednesday and Thursday.
Police and federal agents in Maryland, Virginia and Washington are working around the clock to establish whether the six deaths are linked -- and whether those, in turn, are linked to the Fredericksburg shooting.
If a link is established, then the Washington area is being stalked by murderous sniper whose victims appear to be chosen at random.
There was growing anxiety as the shootings continued.
Authorities in Maryland and Virginia said they would consider Monday whether to close schools and children were not allowed out to play on Friday in Montgomery County, Md. Many people told reporters they were wary of walking on the street and being in the open in shopping areas.
Montgomery County Police Chief Charles Moose said that although the incident in Fredericksburg was too new to comment on, "We think it's important enough to send investigators there."
Moose said that the police are looking for two males, who were seen in the area of one shooting. The men were said to be driving a white delivery truck.
The description of the truck was given to police by a witness at one of the shootings, but Moose said he was "uncomfortable," saying that this individual was the "one and only witness."
Although police said that the FBI wouldn't have a psychological profile of the killer or killers by the end of the day Friday, as previously promised, Moose speculated they were dealing with two males using one weapon.
"My experience would show that you've got one driver and one shooter," he said.
The Bureau of Alcohol, Tobacco and Firearms sent a "geographical profiler" to Montgomery County, Moose said. By looking at maps and "physical boundaries," he said, the profiler hopes to discern a pattern to the seemingly random nature of the killings.
Moose sought to dispel rumors that police had arrested someone in connection with the shooting of Charlot.
Police arrested a man who "needed to be arrested," Moose said, but he was "not connected to the shootings."
Police are "90 percent sure" that the shooter in Maryland was using a high-velocity, .223-caliber bullet and rifle, perhaps mounted with a telescopic sight, fired from a distance, according to a spokeswoman for the Montgomery County police.
There are a number of rifles that utilize this type of bullet, according to the ATF.
"They could have been up to 600 meters away," County Executive Doug Duncan said. That distance would be about 3,600 feet from the victims.
The shooting spree began Wednesday at around 5:20 p.m., when the suspect or suspects fired one shot through a store window, but no one was injured.
Police noted that this window was at a Michaels Variety store and the woman in Virginia was shot in front of a Michaels store.
The first slaying occurred nearly an hour later, after 6 p.m. Wednesday, when James Martin was shot in the parking lot of a Wheaton, Md. grocery store. The store was only two miles away from the Michaels store.
Police described Martin as a 55-year-old white male from Silver Spring, Md.
The next victim was shot and killed on Thursday at about 7:40 a.m. as he was riding a lawnmower at the Fitzgerald Auto Mall. The 39-year-old white male was identified as James Buchanan, of Arlington, Va.
A half-hour later, a taxi driver was killed at a Mobil gas station in the Aspen Hill area. Police identified him as 54-year-old Premkumar Walekar from Olney, Md.
Then at 8:37 a.m., a 34-year-old Hispanic woman, Sarah Ramos, was shot in the head while she was sitting on a bench outside a post office in Silver Spring.
Less than two hours later at a Shell gas station in Kensington, Md. a 25-year-old white female was shot in the back while vacuuming her van. Police said Lori Ann Lewis-Rivera, of Silver Spring, died at the scene.
All the Maryland murders were within a 2.5 mile radius.
(UPI reporter Sharon Otterman contributed to this story.)