Updated

A federal law on serial killings underscores the important investigative role the FBI is playing in the terrifying sniper shootings that have left six people dead and two seriously wounded.

The statute invoked Monday by Montgomery County, Md., Police Chief Charles Moose says the U.S. attorney general and the FBI may look into serial killings if they get a request from the head of a local law enforcement agency.

The law defines serial killings as a series of three or more such crimes, at least one of them committed in the United States.

Moose's request in a letter to Attorney General John Ashcroft follows a substantial amount of assistance from the FBI and the Bureau of Alcohol, Tobacco and Firearms. ATF linked the bullets that struck most of the victims to the same rifle.

Since last week, the FBI has contributed helicopters to help in the investigation, manpower at the police command center and its experts are doing psychological profiling of the killer.

In addition, the FBI is helping out with an investigative tool that involves a computer. It compiles and prioritizes the wide range of investigative leads in the case so that investigators can move quickly at the outset of a complex criminal probe, said Justice Department spokeswoman Barbara Comstock.