Luigi Mangione: Suspect in US healthcare boss killing 'posted about back condition on Reddit for several years'

Mangione, 26, is accused of killing UnitedHealthcare boss Brian Thompson last Wednesday outside the Hilton Hotel in Manhattan.

He was charged on Monday in New York with one count of murder, three counts of criminal possession of a weapon and one count of possession of a forged instrument.

The suspect's attorney has said he intends to plead not guilty to all charges.

Mangione, who attended an Ivy League university, appears to have been active on Reddit since 2016 under the username Mister_Cactus, where he posted about spine health, gaming and travel, according to Sky's US partner NBC News.

Activity on the now-deleted account, which has been archived, matches up with events from Mangione's life, friends confirmed.

Posts focused on a condition called spondylolisthesis.

What is spondylolisthesis?

Spondylolisthesis is where a vertebra, a bone in the spine, slips forward. It can happen anywhere along the spine but is most common in the lower back, according to the NHS.

It can run in families, or can happen as the spine weakens with age. The condition may also be caused by a stress fracture, which is more common in athletes and gymnasts.

Some symptoms include lower back pain that is worse when standing or walking, pain in the bottom or thighs, tight hamstrings and pain or numbness spreading from the lower back down one leg.

The NHS advises anyone suffering from spondylolisthesis to avoid activities that make symptoms worse, such as bending, lifting or athletics. 

Other ways to treat the condition include physiotherapy, taking painkillers, and steroid injections to relieve the pain and numbness.

If these treatments do not work, a GP may refer a patient to a specialist for back surgery. 

The types of surgery include spinal fusion - where the slipped vertebra is joined to the bone below with metal rods, screws and a bone graft - and lumbar decompression, which is a procedure to relieve pressure on the compressed nerves.

Mister_Cactus said in an exchange with another user in April that his condition "went bad to the point where I felt it every day".

In 2018, the account holder wrote about experiencing "restless sleep", describing waking up frequently throughout the night and feeling "unrefreshed no matter how much sleep I get".

Mangione appears to have dealt with back pain since childhood but the problem flared up when he went surfing in recent years, according to a July 2023 post.

"I slipped on a piece of paper and my right glute locked and right leg shut down for a week," a post read.

Mister_Cactus wrote at the time that he had been experiencing issues with his right hip for the past year and a half.

He felt pain while sitting and he had twitching in his leg muscles and sometimes numbness and tingling in his groin, he wrote.

"When my spondy [spondylolisthesis] went bad on me last year it was completely devastating as a young athletic person," Mister_Cactus wrote in a post in August 2023.

The Reddit posts suggest that the account holder underwent spinal fusion surgery in 2023.

Other posts suggest he saw positive results after the operation - he wrote that after a week, he "was on literally zero pain meds" and was able to sit, walk and stand.

A Reddit spokesperson told NBC News the platform's policy is to suspend accounts that may be related to suspects in high-profile criminal investigations, a common practice among tech companies to avoid impersonation or interference in such cases.

-SKY NEWS