Born sometime around 1970, 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 fatally 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 based on Charles Cullen - Both were serial killers and poisoners with jobs as nurses, went undetected for years because they constantly kept switching to different hospitals, and others were blamed for their crimes until the truth was revealed.
Sara also seems to have been based on Stella Nickell - Both were killers, poisoners, and copycats who targeted their husbands for insurance money (though only Nickell succeeded), and both copied the M.O. of at least one other killer (Nickell copied the unidentified Tylenol Killer, while McLean copied the M.O. of poisonings suspected to have been committed by the Russian government) in order to divert attention away from themselves and to cover up their true crimes.
She is also similar to John Allen Muhammad, one of the two D.C. Snipers - Both were killers with a specific M.O., targeted and killed random people, and used these murders to cover up the attempted murder of their true target: their spouses. Both McLean and Muhammad also died at the end of their attacks (though under different circumstances).
- 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)