Before becoming a Psychiatrist , Maj.  Hasans'  undergraduate   major was biochemistry.* Nerve gas  would seem readily produced by one thus  educated, yet he opted ( allegedly) for the far less efficient  guns of the Columbine High School killer teens. Alternatively, counseling soldiers in  the Mid-east would have provided an opportunity to produce multiple “Manchurian Candidates” using  his “professional” skills. But ultimately, given such a background Maj. Nidal Malik Hasan might have used even  more efficient methods without exposing his hand, targeting  a disease against selected individuals or groups  perhaps even altering a disease genetically  to act only against the ethnicity of his  target group(s). Given the diversity of the US  such a method would be complex. Indeed it would be far  easier to implement  against less diverse cultures such as inbred tribal clans of   pure blood. In the alternative accidental death  and/or suicide rates for certain groups could be subtly encouraged by psychological manipulation or influence. Clearly he is deranged and dishonorable, a common characteristic of Far  Right Wing ( Islamic  and other ) zealots and  terrorists, who surrender reason and civilization to  rationalize the urges born of the  reptilian hindbrain. Recall that Lee (and others faced with a clash of loyalties) resigned from the Union Forces before joining the forces of his native state and the Confederacy. *http://www.undergradcatalog.registrar.vt.edu/0708/als/bchm.html