Fact check: Did UnitedHealthcare murder suspect post viral Substack? 

Luigi Mangione, the suspect charged with murder in UnitedHealthcare CEO Brian Thompson’s December 4 shooting death, left a handwritten document explaining his motivation, New York City police officials said.

Police had not released the document to the public as of December 10. But some X users were sharing what they said was a manifesto Mangione published on Substack, a subscription-based platform for online content creators.

“This is allegedly Luigi’s manifesto,” a December 9 X post with more than five million views said. The post shared four screenshots of text from a Substack post with the headline “The Allopathic Complex and Its Consequences” and the subhead “Luigi Mangione’s last words”.

The Substack article was dated December 9, the day Mangione was arrested at an Altoona, Pennsylvania, McDonald’s. “The second amendment means I am my own chief executive and commander in chief of my own military,” it said. “I authorise my own act of self-defence in response to a hostile entity making war on me and my family.”

We found other social media posts sharing the same images or language as the blog post and saying Mangione had written them.

But he did not write them. Substack removed the post “for violating Substack’s Content Guidelines, which prohibit impersonation”, a company spokesperson told PolitiFact in an emailed statement.

New York City Police Commissioner Jessica Tisch said on December 9 that police had found a handwritten document when they arrested Mangione “that speaks to both his motivation and mindset”. As of December 10, authorities had not offered more information about its contents.

The New York Times reported on the three-page document, citing an internal police report it obtained. Mangione described the act as a “symbolic takedown” of the healthcare industry, citing “alleged corruption and ‘power games’”.

None of that language appeared in the Substack post being shared online as Mangione’s manifesto.

PolitiFact reviewed reports about the document by The New York Times, CNN, New York Post or ABC News, all outlets that said they had reviewed the message or had it described to them by law enforcement sources. None of the reports included mention of the Second Amendment. PolitiFact has not obtained a copy.

We rate claims that Mangione wrote the Substack article as False.