Luigi Mangione, the suspect in the murder of UnitedHealthcare CEO Brian Thompson, was reportedly identified by San Francisco police four days before being arrested in Pennsylvania, two sources familiar with the situation confirmed to the San Francisco Chronicle on Thursday (December 12).

Two sources who spoke on condition of anonymity as they aren't authorized to discuss the matter publicly claimed that a San Francisco Police Department Special Victims Unit officer recognized Mangione as potentially being the shooting suspect on December 5, one day after the incident took place, based on the surveillance images showing his face. The officer was reportedly familiar with Mangione as he'd been reported missing to San Francisco police in mid-November and the Special Victims Unit, which was assigned to the missing person's case, reported his identity to the FBI on December 5.

The report contradicts authorities' previous claim that Mangione wasn't on law enforcement's radar prior to being arrested at a McDonald's in Altoona on Monday (December 9).

“This was not a name that was called into us,” New York City Police Commissioner Jessica Tisch told NBC News on Tuesday (December 10).

Mangione, 26, an Ivy League graduate from a prominent Maryland real estate family, was arrested in Altoona after a McDonald's employee spotted him eating at the restaurant and believed he resembled the then-wanted gunman linked to the Manhattan shooting. The suspect was found carrying a ghost gun, masks and a manifesto linked to the incident at the time of his arrest, authorities confirmed.

Mangione was reported to have lost touch with his loved ones in recent weeks, with his mother reporting him missing, possibly from a home in San Francisco, on November 18, law enforcement sources told the New York Post after his arrest. Aaron Cranston, a former classmate at the Gilman School in Baltimore, told the New York Times that Mangione's family sent a message to peers indicating that he hadn't been in touch since undergoing back surgery several months prior while trying to find him earlier this year.

RJ Martin, a friend and former roommate who lived with Mangione in Hawaii, told CNN that the suspect had previously discussed his back issues.

“When I first interviewed him, before he moved in, I remember he said he had a back issue, and he was hoping to get stronger in Hawaii,” Martin said, who claimed the issues were so "traumatic and difficult" that Magnione was bedridden for a week after one basic surfing lesson.

Martin said Mangione sent him images of X-rays after he underwent surgery.

“It looked heinous, with just giant screws going into his spine,” he said.

Several sources indicated that Mangione may have held a grudge against the UnitedHealthcare CEO due to his interactions with the medical industry, having shared an X-ray photo that showed four pins in a spine on his X account, as well as having five books involving chronic back pain on his Goodreads account reading list.