Police Say Suspect’s Notebook Described Rationale for C.E.O. Killing

Luigi Mangione, who has been charged with killing the chief executive of UnitedHealthcare outside a company investors’ day in Manhattan, was arrested with a notebook that detailed plans for the shooting, according to two law enforcement officials.

The notebook described going to a conference and killing an executive, the officials said.

“What do you do? You wack the C.E.O. at the annual parasitic bean-counter convention. It’s targeted, precise, and doesn’t risk innocents,” was one passage written in the notebook, the officials said.

The shooting of the executive, Brian Thompson, occurred early Dec. 4 as Mr. Thompson arrived on West 54th Street outside a Hilton hotel to prepare for the UnitedHealthcare investors’ meeting. His assailant escaped on a bicycle and then disappeared.

Police officials in New York were able to match Mr. Mangione’s fingerprints to those on a water bottle and a Kind snack bar wrapper recovered near the crime scene, Commissioner Jessica Tisch said at a news conference on Wednesday.

Commissioner Tisch said the New York police now have the unregistered gun that was found in Mr. Mangione’s possession when he was arrested in Altoona, Pa., on Monday. The police brought it to the department’s crime lab, where they matched it to the three shell casings that were found at the crime scene, she said. The crime lab confirmed they matched the suspect’s, police officials said in a briefing with reporters on Wednesday afternoon.

The police were also analyzing a bag of bullets found this week in Central Park to see if they were connected to the killing, one of the law enforcement officials said.

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