Luigi Mangione (26) reportedly wrote in a spiral notebook that he decided against staging an explosion in Manhattan because it “could kill innocents”.
Mr Mangione, an Ivy League graduate, is alleged to have written a to-do list in the notebook. The notebook reportedly stated that he would “kill the CEO at his own bean-counting conference”.
Brian Thompson was shot dead on December 4 as he walked into the Hilton Midtown in Manhattan to attend a conference, sparking a five-day manhunt that led to Mr Mangione’s arrest.
Along with a three-page manifesto in which Mr Mangione allegedly said that he acted alone, police found pages of handwritten notes in a spiral notebook.
Among the notes were the musings about possibly using a bomb versus a shooting, CNN reported.
According to The New York Times, the notebook stated: “What do you do?
“You wack the CEO at the annual parasitic bean-counter convention. It’s targeted, precise, and doesn’t risk innocents.”
Fingerprints found at the scene of the shooting were said to match those taken from Mr Mangione after he was arrested in Pennsylvania on Monday.
Police also found other items on Mr Mangione which allegedly linked him to the crime, including multiple fake IDs and the “ghost gun” used in the shooting.
According to CNN, there was an “oblique reference” in the notebooks to how Mr Mangione figured out Mr Thompson’s movements.
Mr Mangione is reported to have written: “This wasn’t that difficult. It was a combination of social engineering and CAD [computer assisted design].”
Mr Mangione’s lawyer suggested his client could plead not guilty to the murder charges in New York.
The suspect is currently detained in Pennsylvania, where he was arrested, on other charges including using a fake ID card.
Speaking to ABC News, lawyer Thomas Dickey said that Mr Mangione, who comes from a wealthy real estate family in Maryland, would deny the charges in Pennsylvania.
Mr Dickey said there was “no evidence” linking his client to the shooting and claimed that “a lot of guns look the same”.
He said: “I have not been made aware of any evidence that links the gun that was found on his person to the crime, so these are things that we’re looking to see”.
In a statement, Mr Thompson’s family thanked him for being a loving parent.
“Brian was a devoted father to our two sons, and we will miss him for the rest of our lives,” they said.
“We appreciate the overwhelming outpouring of kind words and support we have received.” (© Telegraph Media Group Holdings Ltd)