6 Things to Know About UnitedHealthcare CEO's Fatal Shooting: Suspect Luigi Mangione, Conspiracy Theories and More

UnitedHealthcare CEO Brian Thompson was gunned down outside the Hilton hotel in New York City at around 6:46 a.m. on December 4. The New York police said Thompson was walking toward the building before the company's annual investor conference when the shooting took place.

New York Police Department commissioner Jessica Tisch said the gunman, who has since been identified as Luigi Mangione, "was lying in wait" before killing Thompson in Midtown Manhattan.

"Many people passed the suspect, but he appeared to wait for his intended target," said Tisch at a news conference. "I want to be clear: At this time, every indication is that this was a premeditated, preplanned, targeted attack."

Thompson was rushed to Mount Sinai West in critical condition. He was pronounced dead at 7:12 a.m.

UnitedHealth released a statement to address the CEO's death, saying, "We are deeply saddened and shocked at the passing of our dear friend and colleague. Brian was a highly respected colleague and friend to all who worked with him. We are working closely with the New York Police Department and ask for your patience and understanding during this difficult time."

Police recovered three live 9-millimeter rounds and three discharged shell casings at the scene, all of which had words written on them.

According to NYPD officials, the words "delay," "deny" and possibly "depose" appeared on the bullets the gunman used to shoot and kill Thompson. Investigators assumed those could reference "the three D's of insurance": "delay," "deny" and "defend."

NYPD Chief of Detectives Joe Kenny wrote in a statement, "The motive for this murder currently is unknown, but based on the evidence we have so far, it does appear that the victim was specifically targeted. But at this point, we do not know why."

Amid the initial investigation, a source revealed that UnitedHealth Group — UnitedHealthcare's parent company — was aware of the threats against the company's high-level executives.

While there was no mention of the CEO's name, Brian's widow, Paulette Thompson, told NBC News there were some people "that had been threatening him."

She added in a separate statement to CNN, "We are shattered to hear about the senseless killing of our beloved Brian. Brian was an incredibly loving, generous, talented man who truly lived life to the fullest and touched so many lives. Most importantly, Brian was an incredibly loving father to our two sons and will be greatly missed."

The Wall Street Journal later revealed Brian was separated from Paulette at the time of the fatal shooting.

Before authorities were able to identify and locate the shooter, former Maryland state police commander Neill Franklin claimed Brian may have hired the suspect to kill him.

He told CNN host Dana Bash, "It's a good chance. It's a very good possibility with these new photographs, that is, that they already know who he is. It's a very good chance of that. But I also I want to say something else that I know these criminal investigators are looking into as it relates to motive.

Neill noted there have been instances when people plotted their deaths for "certain reasons."

"I'm not saying this is the case, but as an investigator ... Insurance purposes, you know, maybe they fear some type of investigation down the road. Maybe they want to leave their family in a good light. But there have been cases where people have orchestrated their own demise," he continued.

After the targeted killing, NYPD released images and videos of Luigi taken before, during and after the shooting incident.

In a clip, the assailant was seen fleeing by foot through an alley before using an e-bike into Central Park. Police also released images of the alleged shooter smirking while inside the HI New York City Hostel at 891 Amsterdam Ave., where he stayed from November 24 until the morning of the murder.

Five days later, the suspect was identified and arrested in Pennsylvania. A source confirmed he had a similar gun used in the shooting.

CNN chief law enforcement and intelligence analyst John Miller said Luigi had a "manifesto," explaining, "He starts off basically saying 'I don't want to cause any trauma, but it had to be done.'"

John added, "He talks about how these parasites had it coming. [He] really kind of goes into problems with the health industry…talking about the health care industry and the need for violence."

Luigi, an Ivy League graduate, has been charged with murder, two counts of criminal possession of a weapon (loaded firearm), possession of a forged instrument and criminal possession of a weapon (firearm silencer) in New York. He also faces five other charges, including two felony charges for forgery and carrying a firearm without a license, in Pennsylvania.

R.J. Martin, a friend of the shooter, revealed Luigi went "radio silent" and suffered from chronic back pain for months before the killing of Brian.

"Luigi was just widely considered to be a great guy. There were no complaints," R.J.'s spokesperson Josiah Ryan added. "There was no sign that might point to these alleged crimes they're saying he committed."