ROCKVILLE, Md. -- Authorities on Saturday investigated a Virginia shooting for links to a sniper spree that left six dead in Maryland and Washington, D.C., but they said they may never be able to confirm that all the slayings were connected.

No arrests had been made in the scattered shootings that began Wednesday and apparently targeted people at random. 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.

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

But the bullets used in the two other killings "are in very poor shape," Moose said at a press conference Saturday. "We may not be able to link them."

Moose was more hopeful that investigators would find identifiable bullets or bullet fragments in the car of a woman shot Friday in Fredericksburg, Va., about 55 miles south of Rockville.

The 43-year-old Spotsylvania, Va., woman, who was shot in the back in a parking lot, was listed in serious condition at INOVA Fairfax Hospital Saturday.

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 Montgomery County 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.

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 Saturday, and calls to the ATF were not answered.