Sumana Chatterjee

and Seth Borenstein ~ Knight Ridder Newspapers

ROCKVILLE, Md. -- The most detailed and descriptive account to date of the Washington-area sniper, his weapon and his vehicle came from a witness who made it up, authorities said Thursday.

It was the second setback for the investigation in two days. On Wednesday, police said they were unable to develop a composite picture of the sniper because the witness accounts weren't good enough.

Police also criticized the news media for reporting uncorroborated witness descriptions of the suspect and the gun.

The announcements were the biggest developments at a daily media briefing in what continues to be a difficult investigation.

Questionable details

Dismissed Thursday was a claimed witness's report to police and some journalists that he'd seen an olive-skinned shooter wield an AK-74 assault rifle at the latest shooting and drive off in a cream-colored Chevy Astro van with a roof rack and its left taillight out.

"All of the descriptive information" from this source is discredited, said Lt. Amy Lubas, spokeswoman for the Fairfax County Police Department in suburban Virginia.

Authorities kept an upbeat appearance, saying they were following up leads from other witnesses to the Monday night slaying of Linda Franklin, 47, an FBI analyst, in the parking lot of a Home Depot in the Washington suburb of Falls Church, Va. She was the ninth person killed in a 13-day shooting spree that also wounded two others.

"It has not setback the investigation," police chief Charles Moose of Montgomery County, Md., the lead spokesman on the case, said of the recanting witness. "... We are making progress, we remain very optimistic." "We're not discouraged at all," said Michael Bouchard, the head agent on the case from the federal Bureau of Alcohol, Tobacco and Firearms.

"We're one tip away from breaking this case," he added, but didn't elaborate.

Fairfax County police said state and federal prosecutors would determine whether to file charges against the witness who gave them the false report.

Moose said no decision had been made because investigators had higher, more immediate priorities to focus on.

Looking for van

Police are still looking for a white van with a silver roof rack, either a Chevy Astro or a Ford Econoline E-250. Witnesses reported seeing such a van near the scene of at least one earlier shooting.

Authorities also used Thursday's briefing to complain about media reports that lent credence to the false witness's account.

That information is "not reliable," said police chief Tom Manger from Fairfax County.

Authorities did not dispute the reports, but stressed that they don't want information given to the public unless they have corroborated it.

"When we have the media interviewing witnesses, interviewing potential witnesses, and writing stories as a result ... then we get this noise, this confusion out there that I think somehow causes people to have tunnel vision, causes people to focus in on things that are not appropriate," Moose said. "So again, it is a case that there's a lot of interest in, but there also continues to be danger, so we would like the opportunity to do our job." Bouchard said that more than 30 firearms can fire the .223 caliber rounds that police say were used in the slayings, and that a witness could easily mistake one firearm for another from a distance. He did say that the public should keep an eye out for assault-type weapons similar to but not limited to the Colt AR-15, a civilian version of the U.S. military's M-16 rifle.

Media disclosures, accurate or not, are "meaningless" to the investigation, said Florida State University criminology professor Cecil Greek.

"I really don't think in this case what the media's releasing is hampering the investigation," he said. "I don't see in this case how it affects anything he's been doing." For the police, "they feel the less information they give out, the better chances they have of catching the people," Greek said. But at the same time, "there's a huge pressure for them to release information, not just from the media but from the citizenry." In other developments Thursday, a 13-year-old boy who was shot by the sniper 11 days ago and had been in critical condition was upgraded to serious condition, said Washington, D.C. Children's Hospital spokeswoman Kellie Peacock.