Sara was a nurse who worked in the nuclear medical departments of fifteen different hospitals in the Washington, D.C. metropolitan area. She was also a closet psychopath. At some point, she devised a scheme to collect the insurance money of her husband Alex, who she had taken out a $5 million life insurance policy for. Over the past nine years, Sara stockpiled stolen radioactive materials that she had access to, having escaped detection by switching jobs frequently, not stealing from some of the hospitals she worked in, and hacking into the inventory logs of at least five of her workplaces to alter their content. At least four of her former workplaces also assumed the thefts were the work of other employees who were subsequently fired.
After lethally poisoning four people, including Sam Bower, a friend of Stephen's, Sara puts radioactive material in Alex's lunch and lets it poison him. Because she knows that she will be scrutinized if Alex is the last victim in the poisonings, she immediately goes out with a syringe to find another victim to poison. However, the BAU, having deduced the true motive of the attacks, locate her at another federal building. When Prentiss confronts her, Sara grabs a woman and threatens to inject her with the syringe. Prentiss, Lewis, and JJ are unable to take a clean shot, but before she can poison the woman, Rossi shoots Sara from behind, killing her.
Because she wanted to make the poisonings look like the work of Russian assassins, Sara targeted random employees of federal government offices. She would approach them outside of their workplaces and inject radioactive material into their lower backs with a syringe. This would cause them to come down with symptoms of heart attacks, followed by organ failure, thus guaranteeing slow deaths. When she attacked her husband Alex, she didn't inject him with a syringe and instead put the radioactive material in his food as she packaged it. However, he was saved by a gastrointestinal study.
The unsub is inducing symptoms consistent with heart attacks as a diversion from murders by poisoning. This M.O. is consistent with that of assassinations supposedly committed by the Russian government, but three of the four victims are not typical Russian targets. Thus, it is believed that the unsub is copying this M.O. in order to obscure their true motive for the killings.
This kind of unsub is either an embittered federal employee who was fired, forcibly retired, or otherwise rendered obsolete; someone who intends to profit off of marketing an antidote to the poison once it is discovered; or someone with a personal grudge that is totally unrelated to the federal government, who is using a politically-charged M.O. to divert attention away from said grudge. The unsub also shares characteristics with known product-tamperers and is unconcerned about possible collateral damage as long as they help divert attention away from the true motive of the poisonings. At this point, the unsub does not believe law enforcement is on to him, and media coverage on the poisonings will not be released so as to prevent copycat incidents.
Sara seems to have been inspired by Stella Nickell, a woman who filled several capsules of Excedrin with lethal cyanide and distributed the tampered bottles throughout a number of stores. Much like Nickell, Sara was hoping to kill her husband, undetected, through the poisonings in under to collect his insurance money, since authorities would be convinced they were looking for a serial killer targeting random people. Also, Nickell copied the Tylenol Killer's M.O., while Sara copied the M.O. of poisonings suspected to have been committed by the Russian government; both did so in order to further divert law enforcement attention from her.
Also, Sara's plan to kill random people and disguise the motive of her husband's death seems to be based on a theory that John Allen Muhammad planned to kill his ex-wife and use the Beltway Sniper murders to hide his connection to her, and therefore the motive behind her death.
In addition, the ways Sara was known to have escaped detection while stealing radioactive material from her workplaces seem to have been taken from Charles Cullen. Like Sara, Cullen was a nurse whose crimes were initially never connected and went undetected for years because he constantly kept switching to different hospitals. Also, one of Cullen's murders was initially suspected on another employee.
- April 3: Aidan O'Harrell (survived, but died in a hospital the next day)
- April 6: Charlene Jorreff
- April 13:
- April 14:
- Benjamin Vargas
- Alex McLean (her husband; attempted, but survived; was poisoned by ingested radioactive material, but cured in time)
- Several unnamed neighbors (indirectly attempted; unintentionally dumped radioactive materials down the water system)
- Unnamed woman (held hostage and attempted to poison)