Accused CEO killer Luigi Mangione faces court as New York police ...
New York police say they'll investigate whether chronic back pain could be part of the reason Luigi Mangione allegedly killed a healthcare executive in Manhattan last week.
They've also released more detail about the accused killer's "handwritten manifesto" as they seek his extradition from Pennsylvania to face a murder charge.
Mr Mangione, 26, is accused of fatally shooting UnitedHealthcare CEO Brian Thompson on the footpath outside a hotel on Wednesday morning, local time.
He has been denied bail a second time during a court hearing in central Pennsylvania, a day after a public tip led to his arrest at a nearby McDonald's restaurant.
As he was led into court by a group of law enforcement officers, he yelled to waiting media about something being an "insult to the intelligence of American people".
Luigi Mangione yelled to media outside the courthouse in Pennsylvania. (Getty Images: Jeff Swensen)
Inside, his lawyer told the court he intended to fight his extradition to New York. That will trigger a formal process that could last weeks, though he is unlikely to succeed in preventing his eventual transfer, according to legal experts.
Multiple US media outlets reported that friends of Mr Mangione had confirmed he had been suffering from significant back pain.
Hawaii man RJ Martin told CNN he recently lived with Mr Mangione in Honolulu, where he saw him struggle with a back problem.
"I know it was really traumatic and difficult," he said. "When you're in your early twenties and you can't do some basic things it can be really, really difficult."
Luigi Mangione was arrested after he was spotted at a Pennsylvania McDonald's. (Supplied: Pennsylvania State Police)
Mr Mangione had also tagged several books about coping with back pain on the review website Goodreads, the New York Times reported. His X profile displayed an image of a spinal X-ray, showing what appeared to be surgical implants.
Asked about the reports Mr Mangione had a back injury and whether that could have played a role in the killing, New York police commissioner Jessica Tisch said: "This is all going to be part of this investigation."
New York Chief of Detectives Joseph Kenny said he had read the manifesto that Mr Mangione was carrying when he was arrested, and it showed he was "frustrated with the healthcare system in the United States".
"Specifically, he states how we are the number one most expensive healthcare system in the world, yet the life expectancy of an American is ranked 42 in the world," Chief Kenny told Good Morning America.
"So he was writing a lot about his disdain for corporate America and in particular healthcare."
Luigi Mangione has been held in custody in Pennsylvania. (Supplied: Pennsylvania State Police)
Mr Mangione has been charged with murder in the second degree and four weapons offences in New York. He also faces weapons charges in Pennsylvania.
An arrest warrant released by the New York courts outlines some of the evidence against him.
It says CCTV captured him checking into a Manhattan hostel at 11:20pm on November 24.
Ten days later, CCTV recorded him leaving the hostel 70 minutes before the shooting, wearing the same clothing as the killer.
Brian Thompson was shot dead out the front of a Manhattan hotel. (Supplied: UnitedHealth Group via AP)
Hostel records show he checked in with a New Jersey driver's licence with the name Mark Rosario on it, the warrant says. He gave the same fake ID to a police officer at the Pennsylvania McDonald's where he was arrested.
A police officer who searched his belongings then found "a semi-automatic pistol with what appears to be a 3D printed loaded receiver with a metal slide and silencer, and written admissions about the crime".
