FBI's Theory On Anthrax Is Doubted "A significant number of scientists and biological warfare experts are expressing skepticism about the FBI's view that a single disgruntled American scientist prepared the spores and mailed the deadly anthrax letters that killed five people last year. These sources say that making a weaponized aerosol of such sophistication and virulence would require scientific knowledge, technical competence, access to expensive equipment and safety know-how that are probably beyond the capabilities of a lone individual."