"We live in a time of war and WMD proliferation. If you continue to be blind to our lack of preparedness, then Americans will die, and I will have no problem in pointing the blame at you!"
Nichols studied anthrax at Fort Detrick and was highly respected in the defense community. After the 2001 Amerithrax attacks occurred, leaving five people dead, he became fanatical and proposed a large and highly unorthodox $50 billion project to defend against further attacks. The plan included supplying every home with gas masks and a two months' supply of ciprofloxacin (an antibiotic commonly used to treat anthrax infections) for each resident and providing all hospitals in major cities with biosafety decontamination capabilities. During a classified meeting on January 31, 2002, with the National Defense Committee, Senator Baylor, the head of the committee, declared that spending that much money and effort at preparing for an attack that may or may not happen was completely unrealistic, and that such preparations would incite fear and panic among the public. Nichols had an outburst, shouting that the U.S. needed to live in constant, fearful vigilance of their enemies and that he would put the blame on the committee if another attack happened. Due to his instability and fanatical nature, he was later demoted to working with the influenza for Bio-Design Technology, one of Fort Detrick's subcontractors, with any other opportunities at holding prominent positions being railroaded. He later divorced his wife. At one point, presumably before his demotion, Nichols wrote a classified study about anthrax terrorism which included a mock anthrax attack on the D.C. train systems.
Before Amplification, a University of Maryland public policy student named Chad Brown had requested Nichols's help with a thesis paper. Nichols became his mentor, having missed teaching, and even produced a new, more hazardous strain of anthrax together with him. Some of Nichols's opinions, including elements from his 2002 proposition, were included in the thesis. Chad decided to take Nichols's beliefs to the extreme, attacking a bookstore he once worked at using the anthrax in an attempt to prove a point. When Nichols found out about it, the two had an argument and then apparently a fight, which resulted in Chad killing Nichols. Because the anthrax dose was very large and powerful, the victims died before the symptoms of anthrax poisoning became present and the attack was never identified as such, instead being pointed to meningitis. Chad then went on to perform a larger anthrax attack on the local park, which infected a total of 25 people. Near the end of the episode, it was deduced by Reid (who had been infected by a dose of anthrax that was opened up during the fight between Nichols and Chad, which was then accidentally left behind) that Nichols kept a cure for the anthrax in a safe place: his own inhaler. The cure would then be administered to Reid and the four last surviving victims of the park attack, while Chad is found and arrested before he could commit another attack.
The BAU were led to Nichols through the profile created from Chad's attacks. It is said that because the targeted locations are not symbolically significant, the attacks are likely be personal, which strongly indicates a homegrown terrorist. Like the Amerithrax case, this is someone from the science or U.S. Defense community and may also be known to other communities. These types of terrorists are myopic zealots, ideologues that believe that their work is of the greatest importance, and may have preached about the threat of an attack on America. His coworkers would describe him as very histrionic, paranoid, and secretive.
He may have logged excess hours at work in the past weeks preparing for the attack. He has taken the full dosage of anthrax vaccines over the recommended eighteen-month schedule and had yearly boosters. This unsub has his own work space where he develops his products in privacy, has access to large and expensive industrial-grade equipment at work, and has written about the threats of anthrax attacks in published papers, yet he feels that no one is listening and that angers him. He may have experienced some sort of professional humiliation, like being demoted or fired, which was his trigger. He may have also betrayed his loved ones to this cause, possibly being recently separated or divorced. He has intimate knowledge of every detail of the Amerithrax case and has talked about what that suspect did right or wrong. He is also watching the news closely to see how the country reacts.