As a man of science, Zawahiri was interested in the use of biological and chemical warfare. In a memo from April of 1999, he observed that "the destructive power of these weapons is no less than that of nuclear weapons," and proposed that Islamic Jihad conduct research into biological and chemical agents. "Despite their extreme danger, we only became aware of them when the enemy drew our attention to them by repeatedly expressing concern that they can be produced simply," he noted. He pored over medical journals to research the subject, and he met with an Egyptian scientist in Afghanistan, Medhat Mursi al-Sayed, whose Jihad name was Abu Khabab. C.I.A. officials believe that Khabab prepared the explosives for the bomb that hit the Egyptian Embassy in Islamabad. Khabab supervised elementary tests of nerve gas; satellite photos purportedly show corpses of dogs scattered about one of the camps near Tora Bora, and Al Qaeda training videos recently acquired by CNN show that poison gas had been tested on dogs. "We knew from hundreds of different sources that Al Qaeda was interested in biological and chemical weapons," says Richard A. Clarke, who was the Clinton Administration's national coördinator for counterterrorism in the National Security Council and is now in charge of cybersecurity for the N.S.C. Clarke told me that in one of the camps human volunteers, wearing protective clothing, were exposed to chemicals in tests similar to ones that the U.S. Army has conducted. During the invasion of Afghanistan, American forces discovered a factory under construction, near Kandahar, that intelligence officials say was to be used for the production of anthrax. A sample of anthrax powder was reportedly found in Zawahiri's house in Afghanistan. According to reports from Israel and Russia, bin Laden paid Chechen mobsters millions of dollars in cash and heroin to obtain radiological "suitcase" bombs left over from the Soviets. He declared in November, 2001, "We have chemical and nuclear weapons," and vowed to use them "if America used them against us."
http://www.fas.org/bwc/news/anthraxreport.htm
This fas.org webpage details the facts surrounding the anthrax attack which our nation sustained nearly one year ago. The dates were interesting reading, as well as the facts surrounding some of the threats.
Originally, based on discussion around Free Republic, I had concluded that the anthrax attack could not have been launched by a fellow American citizen. However, many of the scientific clues substantiate the index of suspicion that a person in the US did the attacking.
It's very interesting reading. FAS seems to suggest that the perpetrator was an American. I'm not so convinced because if the anthrax was US in origin, where did he store the stuff? It's not an innocuous amount of stuff to store. FAS does appear to agree that the source was a government financed source, though perhaps not US.