Luigi Mangione, the suspect in the ambush killing of UnitedHealthcare’s CEO, was not insured by the company, the overarching business that owns it said.

There is no record that Mangione, 26, was ever insured by the company, UnitedHealth Group said.

Mangione is the suspect in the fatal shooting of CEO Brian Thompson on a New York City street on the morning of Dec. 4, as Thompson was walking to a hotel where an investor conference was being held.

The killing remains under investigation.

New York Police Chief of Detectives Joseph Kenny said Mangione’s social media and writings indicate he suffered a painful back injury that was a “life-altering injury.”

Kenny said Mangione may have targeted Thompson because of the size of UnitedHealthcare.

“We have no indication that he was ever a client of United Healthcare, but he does make mention that it is the fifth-largest corporation in America, which would make it the largest health care organization in America,” Kenny said in an interview that aired Thursday.

“So that’s possibly why he targeted that company,” Kenny said.

Mangione was arrested Monday at an Altoona, Pennsylvania, McDonald’s after he was recognized from photos distributed by police, authorities said.

When he was arrested, police found a gun and a silencer, a handwritten document that refers to the health care industry and a notebook, officials have said.

The three-page handwritten document includes the phrase “these parasites simply had it coming,” law enforcement sources have told NBC News.

Mangione also had a notebook in which he is alleged to have written about targeting a CEO, two sources familiar with the investigation said. Archived social media posts appear to show him discussing debilitating back pain.

Thompson was walking on a sidewalk in midtown Manhattan around 6:44 a.m. when a gunman wearing a mask and a hooded jacket shot him from behind and then continued to fire, security video shows.

The killing was targeted, police said. Police have said they believe Mangione arrived in the city by bus on Nov. 24 and stayed at a hostel.

The gun that was recovered when Mangione was arrested has been matched to shell casings found at the scene of the killing, police said Thursday.

The gun was a so-called ghost gun, which was made with a receiver from a company and then built using a 3-D printer, Kenny said.

Mangione is being held in Pennsylvania, where he has been charged with a weapons charge, forgery and other counts, and is fighting extradition to New York. The next hearing in the Pennsylvania case is scheduled for Dec. 30.

New York police said Mangione will be brought back to New York, arrested and charged with murder in Thompson’s killing.

Mangione’s attorney has said he intends to plead not guilty to all charges.