The news from the doctors was terrifying. Both of the postal workers were suffering from an acute infectious disease caused by the bacterium known as anthrax - most commonly found in livestock. In humans, the disease can be spread in three ways: by skin contact, through ingestion or by inhaling the spores. Inhalation anthrax is fatal 95 percent of the time - and it was those dreadful odds that confronted Leroy Richmond and Norma Wallace. Miraculously Leroy and Norman survived but anthrax would eventually strike sixteen other victims and claim five lives.

America came face to face with the specter of bi-terrorism in the days following September 11th. Letters laced with anthrax were sent to NBC News and the New York Post. They had been mailed from Trenton, New Jersey. Two weeks later, anthrax claimed its first victim: 63-year-old Robert Stevens, a photo editor for a tabloid newspaper in Florida called The Sun. The exposure was traced to an opened letter. Initially the investigation targeted Osama bin Laden; however, FBI profilers have concluded that the attacks were probably not the work of international terrorists - but rather, someone right here at home.

Authorities believe the spores probably came from one of two labs. Meanwhile, with no assurance the elusive killer has ties to either of these facilities, the manhunt continues at home and abroad. A $2.5 million reward is being offered for information leading to the arrest and convictions of the person or persons behind the anthrax attacks.

If you have any information about this case, please contact the FBI or call the Unsolved Mysteries hotline, 1-800-876-5353.