Rockville, Md. ? The bullet used to shoot a Virginia woman matches ammunition used to kill at least four of six victims of a sniper spree in Washington, D.C., and suburban Maryland, investigators said Saturday.

Tests conducted by the Bureau of Alcohol, Tobacco and Firearms confirmed that the same weapon was used in five of the random shootings over the past three days in Montgomery County, Md., and Washington. Tests were still under way to determine any links to two additional shootings in Maryland.

“The round that we collected there is in fact a match to the rounds that were used here in Maryland and also in D.C.,” said Maj. Howard Smith, of the Spotsylvania County, Va., sheriff’s office.

The 43-year-old Spotsylvania woman was shot in the back in a craft store parking lot in Fredericksburg, Va., about 55 miles south of Rockville, at about 2:30 p.m. Friday.

No arrests had been made in the scattered shootings that began Wednesday. Authorities were talking to one man late Saturday afternoon, but they stressed that he was not a suspect and no weapons were found with him.

In the Washington suburbs where the killings occurred, police still encouraged residents to go about their normal lives and enjoy their weekend.

“The community is safe for the moment,” Montgomery County Police Chief Charles Moose said earlier Saturday.

Authorities said late Friday that .223-caliber bullets used to kill four of the victims came from the same weapon, perhaps a hunting or assault rifle.

But the bullets used in the two other killings “are in very poor shape,” Moose said. “We may not be able to link them.”

The Virginia victim was hospitalized in serious condition Saturday at INOVA Fairfax Hospital, officials said.

Bouquets of flowers and a teddy bear cover the bench where Sarah Ramos, 34, sat when she was shot and killed Thursday in Silver Spring, Md.

The five victims in the Washington suburbs were gunned down in broad daylight in public places during a 16-hour span Wednesday evening and Thursday morning: two at gas stations, one outside a grocery, another outside a post office and the fifth as he mowed the grass at an auto dealership.

Thursday night, a 72-year-old pedestrian in Washington was shot to death as he stood on a street corner.

Each victim was shot once from a distance. There were no known witnesses to the killings.

Montgomery County police said about 100 of its investigators were following up on about 600 credible tips. They were working with federal law enforcement to search for two suspects they believe fled in a white box truck with black lettering on the side.

Moose said late Saturday afternoon that a 33-year-old Rockville, Md., man who had been listed as missing and who police wanted to talk to about the case was in custody in Fairfax, Va., on an outstanding auto theft warrant from Florida.

“We’re having conversations with the gentleman at this time,” Moose said. He stressed that the man was not a suspect. He added that police traced a weapon that had once belonged to the man, but that he had returned the weapon to a store and someone else bought it.

The News & Observer of Raleigh, N.C., had reported in its Saturday editions that the Bureau of Alcohol, Tobacco and Firearms had issued a bulletin for the man, who had lived in Raleigh and was described as affiliated with militia and white supremacist groups.

FBI agent Chris Swecker in Charlotte, N.C., could not immediately confirm details about the man.

Late Saturday, police said they were investigating the death of a man whose body was found in Howard County, which neighbors Montgomery County. A fisherman found the man, an apparent shooting victim, police said.