After the blood-soaked morning of Oct. 3, when four people were slain by sniper fire in quick succession in Montgomery County, investigators hunting for the killer focused on what seemed their best lead: Witnesses reported seeing a white box truck driving away rapidly from more than one of the shooting locations.

That now-famous but still mysterious truck, and a white van that other witnesses later reported seeing near the scene of a Virginia sniper attack, became embedded in the public's consciousness. Day and night, composite images of the vehicles were broadcast on television, as police across the region made traffic stops with guns drawn, and officials implored people to watch for white trucks and vans being driven suspiciously.

For reasons not fully explained by authorities, however, a different vehicle described by different witnesses after another shooting got relatively little attention. About 12 hours after the last Oct. 3 victim in Montgomery was shot, a man was gunned down in Northwest Washington in an attack soon linked by ballistics tests to the earlier shootings. In that case, witnesses reported seeing an older-model, dark automobile -- at least one said it was a Chevrolet Caprice -- that looked suspicious.

More than three weeks after sniper suspects John Allen Muhammad and John Lee Malvo were arrested in just such a car -- a battered, dark blue 1990 Caprice -- the question lingers: As sniper victims continued falling through October and the search for the gunman grew increasingly desperate, why did police seldom mention the Caprice?

The answer depends on whom you ask.

"We can go back and say why we did this or that as different information comes out," said Officer Derek Baliles, a Montgomery police spokesman. In the early days of the sniper investigation, he said, the white box truck "was our best, most reliable information. We stand by that, and we're not embarrassed by the lookout we provided."

As for why authorities did not also saturate the airwaves with descriptions of the car seen in Washington, Baliles said, "That's a question for D.C. police."

In response, D.C. Police Chief Charles H. Ramsey cited the emphasis placed on the white truck -- and later a white van -- by the Montgomery-based sniper task force led by county Police Chief Charles A. Moose. As officials continued urging the public to be on the lookout for such vehicles -- ubiquitous on area roads -- the task force received more and more tips about trucks and vans, especially after shootings.

"Everybody [said], 'White van this, white van that,' " Ramsey recalled. "Everything that came up from every scene [was] white vans and white trucks."

After Pascal Charlot, 72, was fatally shot in Northwest Washington about 9:20 p.m. Oct. 3, a detective interviewed two witnesses who gave nearly identical descriptions of a suspicious vehicle in the area at the time of the attack, according to a police report. It was a dark, older-model, four-door Caprice with tinted windows, one witness said. The other said it was a big, dark, American-made, square car. They said they saw it drive away with its lights off after Charlot was slain.

Ramsey said officers were told to be on the lookout for a vehicle matching that description. Yet several times during October, police in the region spotted Muhammad's Caprice and did nothing. Because the old car looked suspicious, police ran computer checks of its New Jersey license plate. But the vehicle had not been stolen, and there was no record of it being wanted in connection with a crime.

Muhammad purchased the Caprice for $250 in New Jersey on Sept. 10. Authorities allege that he and Malvo used it in the sniper attacks throughout October.

D.C. police did not issue a composite image of the car that witnesses reported seeing the night Charlot was slain. So the only pictures of possible suspect vehicles that reached the public were images of a box truck and van.

A week after Charlot was shot, when Moose was asked in a CNN interview about the vehicle described by the witnesses in the District, he played down the reports, saying there was "not a big push for public feedback on that."

Katheryn Russell-Brown, an associate professor of criminology and criminal justice at the University of Maryland, said authorities should not be faulted for releasing composite images of the van and truck. "Police had witnesses," she said. "They were checked out, and this is what they said they saw."

Authorities also said they wondered throughout the investigation why no innocent driver of a white box truck came forward to say he or she had been in the area of the Montgomery shootings Oct. 3. Investigators said they were made suspicious by the fact that no such driver emerged after days of publicity about the truck.

As for the white van, Moose said in a CNN interview that "we did have a couple of situations in two different shootings where people with vehicles similar to this actually said, 'Yes, I was in the area there.' They stopped at their local police station. They explained what they were doing."

Meanwhile, the Caprice stayed on investigators' back burner.

On Oct. 14, when Linda Franklin, 47, was fatally shot outside a Home Depot in Seven Corners, District police stopped traffic on the 14th Street bridge as part of a wide dragnet after the shooting. But as one law enforcement official noted, police were interested in white trucks and vans.

"A Chevy Caprice could have gone right by us," the official recalled. "We spent four hours on the bridge . . . and we were looking for the wrong kind of thing."

Composite images of a box truck were shown in newspapers and on television during the October sniper attacks across the region.