Luigi Mangione laid out a chilling blueprint that reveals why he felt it necessary to allegedly gun down UnitedHealthcare CEO Brian Thompson in December 2024 — and his reasoning is scrawled out in a red spiral notebook, new court documents reveal.

According to his “manifesto” — revealed in a new court filing from Manhattan District Attorney Alvin Bragg and obtained by the New York Post — 27-year-old Mangione’s disgust with the insurance industry — which he wrote “extracts human life force for money” — was the driving force behind his desire to make a political point while harming as few people as possible.

He penned … “So say you want to rebel against the deadly, greed fueled health insurance cartel. Do you bomb the HQ? No. Bombs=terrorism.”

The so-called “model prisoner” jotted down his thoughts on Oct. 22, just six weeks before he allegedly offed Thompson outside a Manhattan hotel. He was arrested five days later, and the handwritten playbook was discovered in his backpack.

Even more disturbing … despite Mangione wanting to avoid hurting “innocents,” he allegedly hatched a plan for a mass-casualty event in his home state of Maryland. He reasoned it “would’ve been an unjustified catastrophe that would be perceived mostly as sick, but more importantly unhelpful.”

It’s not clear exactly what his plan was, but he was reportedly “glad” he procrastinated because it allowed him to focus on learning more about UnitedHealthcare … and make his point with some morality still in place.

Exposing more of his driving points, Mangione reportedly wrote killing Thompson at an annual investors conference — the late CEO was at the New York Hilton Midtown Hotel for UnitedHealth Group’s annual investor meeting — “conveys a greedy bastard that had it coming” and therefore would be more well-received by the public.

He also allegedly reveled in the idea of UnitedHealthcare taking a hit financially due to the ordeal.

Even more … Mangione was found with a note directed to the federal government when he was arrested, which was included in the new filing by prosecutors.

In his alleged candid letter, he claimed he was not working with anyone else and that he engineered the entire plot on his own.

And while he reportedly apologized for “any strife or trauma” he caused, he said it “had to be done,” adding … “Frankly, these parasites simply had it coming.”

Mangione is currently being held at the Metropolitan Detention Center in Brooklyn, New York.

His next court appearance will be on June 26, with a federal trial expected some time in 2026.