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A disturbing new development has emerged in the ongoing case against Luigi Mangione, the man accused of assassinating UnitedHealthcare CEO Brian Thompson in December 2024. According to court documents unsealed on June 5, 2025, authorities discovered a handwritten notebook in Mangione’s backpack at the time of his arrest. Prosecutors describe the notebook as a manifesto, filled with detailed notes that outline Mangione’s motivations, ideological beliefs, and a step-by-step plan to target Thompson. The contents of the notebook, officials say, leave little doubt that the attack was premeditated and intended as a political statement against the U.S. health insurance industry.
Mangione reportedly began drafting his plans months before the attack. In passages cited by investigators, he accused health insurance companies of operating as part of a “greed-fueled cartel” and stated that UnitedHealthcare “checks every box” as a symbol of systemic corruption. He likened his ideological stance to that of Ted Kaczynski, the infamous Unabomber, but noted he rejected the idea of mass casualties. Instead, Mangione appeared to favor a more targeted, symbolic act—one he believed would draw national attention and spark discussion about the failures of the American healthcare system.
The notebook also revealed that Mangione initially considered building an explosive device, but eventually settled on an assassination to avoid harming innocent bystanders. He specifically chose a high-profile investor event in New York City to carry out the attack, according to the documents. Alongside the notebook, law enforcement recovered bullet casings engraved with the words “Deny,” “Depose,” and “Delay,” which prosecutors argue reflected Mangione’s view of the health insurance industry’s treatment of policyholders. Surveillance footage reportedly shows Mangione trailing Thompson the night before the fatal shooting, adding further weight to the state’s case for premeditation.
Prosecutors say the notebook is central to their effort to classify the crime as a form of domestic terrorism. They argue that Mangione was not acting out of personal rage, but rather pursuing a political goal—one aimed at intimidating or coercing public institutions. Federal officials are also reviewing the case and are reportedly considering seeking the death penalty. Mangione has pleaded not guilty to charges of murder, terrorism, and stalking. His defense team has filed a motion to suppress the notebook as evidence, claiming it was obtained without a valid search warrant. That motion is expected to be ruled on later this month.
Public reaction to the revelations has been sharply divided. Some see Mangione’s writings as the product of a disturbed individual, while others frame them as a radical form of protest against a deeply flawed healthcare system. His notes include references to healthcare affordability, patient denial rates, and profit-driven policies that, he argued, contribute to unnecessary suffering and death.
