I think it was Saddam using a proxy.
Only four countries have weaponized anthrax. If it was domestic, the FBi would have a lead by now.
This strain came from a Department of Defense lab (USAMRID), hence it WAS domestic.
It could have been one or more of the 9/11 terrorists, or someone working with them.
But FBI never likes to admit to terror ops in the conus, look at WTC I, where top government officials were thinking that the truck bomb was "a transformer fire" for a day or so.
I suspect the Anthrax Vaccine industry. There is $Billions to be made by vaccinating every US citizen.
In 1997 the DOD let a no bid contract to Bioport for $150 million just to vaccinate the 28,000 troops rotating through the Persian Gulf. Imagine what the price tag would be to vaccinate 240 million americans?