ROCKVILLE, Md. -- The old Chief Charles Moose was reassuring, urging people to carry on with their routines despite the sniper roaming the Washington area.

The new Moose offers no such comfort: ''Your children are not safe, anywhere at any time,'' the Montgomery County police chief said Tuesday, quoting a note apparently written by the sniper as part of an increasingly public dialogue with a man suspected of killing at least nine people and wounding three.

The chilling words were left at the scene of Saturday night's shooting in Ashland, Va. The chief, leader of the multi-agency task force investigating the shootings, repeated them 11 hours after bus driver Conrad E. Johnson, 35, was shot to death in Aspen Hill while preparing to begin his morning route.

Authorities suspect Johnson is the sniper's 13th victim, although confirmation awaits ballistics tests. The federal Bureau of Alcohol, Tobacco and Firearms was examining the bullet at its lab in Rockville.

Moose also issued a plea to the killer, urging him to continue a dialogue that began after Saturday's shooting.

''It is important that we do this without anyone else getting hurt,'' Moose told reporters Tuesday evening in comments directed at the sniper.

Authorities received the latest message from a person they believe to be the killer after Tuesday's shooting, a source familiar with the case told The Associated Press. The Baltimore Sun, citing unidentified sources, reported that a letter left Tuesday at a park near the shooting repeated demands first made in Saturday's note.

A senior law enforcement official, speaking to The Associated Press on condition of anonymity, said Saturday's note demanded $10 million.

''We have researched the options you stated and found that it is not possible electronically to comply in the manner that you requested,'' Moose said in a message that authorities said would be understood by the sniper. ''However, we remain open and ready to talk to you about the options you have mentioned.''

He said the sniper was seeking an 800 telephone number to talk with authorities. Moose offered to set up a private post office box ''or another secure method'' if the killer preferred.

''You indicated that this is about more than violence,'' Moose said. He did not answer reporters' questions about the statement, the longest he has made to the suspect.

The bus driver was gunned down in the same community where the shootings began Oct. 2. If the latest attack is confirmed, the sniper will have killed 10 people and critically wounded three others in Maryland, Virginia and Washington.

The warning about children's safety was discovered by police outside a Ponderosa steakhouse just north of Richmond, Va., where the sniper critically wounded a man Saturday night. Moose said the warning was a postscript, but refused to describe the rest of the note.

The letter writer also called police inept and described six unsuccessful attempts to reach investigators by telephone since the attacks began, The Washington Post reported, citing sources it did not identify. Those sources said the letter was tacked to a tree.

In Virginia, more than 140,000 students in the Richmond area were to return to school today after a two-day school closure prompted by Saturday's shooting.