Tuesday, October 22, 2002 Posted: 5:04 AM EDT (0904 GMT)

RICHMOND, Virginia (CNN) -- Investigators believe the sniper who has terrorized the greater Washington area called authorities Monday morning using a voice-disguising device, a source close to the investigation told CNN.

It was that phone call, this source said, that prompted Montgomery County Police Chief Charles Moose to urge the possible sniper to "call us back."

"The person you called could not hear everything that you said. The audio was unclear, and we want to get it right. Call us back so that we can clearly understand," Moose told reporters at an afternoon news conference.

To members of the news media, Moose said: "If you could carry that message clearly and carry it often, it would be greatly appreciated."

Moose would not elaborate on police attempts to communicate with the sniper, saying to do so "would be inappropriate and detrimental to our investigation."

Earlier Monday, police spokeswoman Lucille Baur called the situation "very fluid."

"We're in a very sensitive stage in the investigation," she said.

It was the third statement from Moose in two days in which he has tried to communicate with the messenger about the sniper blamed in the killings of nine people and wounding of three others in the Washington area since October 2.

Moose first sought contact Sunday after a handwritten note was found behind the Ponderosa Steakhouse where the latest sniper victim was shot Saturday. Moose addressed that plea to "the person who left us a message at the Ponderosa."

The note "hinted at a demand for money" and threatened "more killing," law enforcement sources said Monday.

Sources said investigators found the note after a caller to the sniper tip line indicated there was a note for police in the woods near the restaurant. Sources said the caller was a man with "an accent of unknown origin."

The sources would not elaborate on the specific language used in the letter, which is undergoing analysis at an FBI lab for DNA, handwriting and other details that might help determine who wrote it. They said they were working under the assumption that it is from the sniper.

The sources said authorities were comparing the letter and the handwriting to a message on a tarot card found near a middle school in Bowie, Maryland, where a 13-year-old boy was critically wounded October 7. That message said, "I am God."

The handwriting, at least initially, did not appear to match, the sources said.

-- Anonymous, October 22, 2002