BALTIMORE (AP) - A tarot card with the taunting words "Dear policeman, I am God" and a shell casing emerged yesterday as potential clues in the hunt for the sniper terrorizing Washington's suburbs.

The card and casing were found near a middle school in Bowie, where a 13-year-old boy was critically wounded by the gunman Monday, a source familiar with the investigation said on condition of anonymity.

Authorities said the shell was .223-caliber, the same kind of bullet used to kill six people and wound another in Washington and its Maryland and Virginia suburbs in the last week. The casing is believed to be the first one recovered since the slayings began.

Michael Bouchard, an agent with the Bureau of Alcohol, Tobacco and Firearms, would not say whether authorities had linked the casing to the attacks.

Montgomery County Police Chief Charles Moose also wouldn't comment when asked about the tarot card, and angrily suggested unapproved information had been leaked.

"I need to make sure I don't do anything to hinder our ability to bring this person or these people into custody," Moose said.

The message left on the tarot card called the Death card was first reported by WUSA-TV and then by The Washington Post. Police sources told the newspaper the items were found 150 yards from the school in a wooded area on matted grass, suggesting the gunman had lain in wait.

Tarot cards, used mainly for fortunetelling, are believed to have been introduced into western Europe by Gypsies in the 15th century.