Person of interest caught in connection to the killing of United Healthcare CEO

Police are questioning a person in connection with the killing of UnitedHealthcare CEO Brian Thompson.

On Wednesday (December 4) at 6:46am, Thompson was shot outside of the Hilton Hotel in Manhattan, New York.

Footage was released by authorities of the CEO's alleged killer and sources have since revealed to NBC News that a person has been brought in for questioning in Altoona, Pennsylvania.

Footage released by police showed the moment a person armed with a gun approached Thompson from behind and began shooting.

Thompson could be seen falling to the floor, the shooter fleeing the scene by electric bike.

On Wednesday, New York Police Commissioner Jessica Tisch told reporters authorities believe the attack was 'premeditated, preplanned' and 'targeted,' the shooter appearing 'to wait for his intended target'.

Paulette Thompson told NBC News that her husband had been receiving 'some threats' and the words 'deny,' 'defend' - or police stating 'delay' - and 'depose' were later discovered written on the shell casings.

NYPD chief of detectives Kenny said: "Based on the evidence we have so far, it does appear the victim was specifically targeted. But at this point, we do not know why."

After sharing footage, police also released further photographs of the attacker asking for the public's help and offering a reward of $10,000 for information 'leading to an arrest and conviction'.

And sources have revealed a man has since been brought in for questioning.

Brian Thompson was shot on December 4 (UnitedHealth Group)

The person in question was picked up by authorities at a McDonald's in Altoona after he was spotted acting 'suspiciously'.

The person who has been brought in for questioning is reported as having allegedly been found with a gun similar to that used in the killing of Thompson alongside a silencer, sources said.

Thompson's suspected shooter is also believed to have arrived in New York in late November and stayed in a hostel in Manhattan under the name 'Marc Rosario,' police said.

Two senior law enforcement officials told NBC News that the man who has since been brought in for questioning was also found carrying a fake Nevada Jersey ID with the name 'Marc Rosario'.

The person of interest has not been arrested or charged.

A senior law enforcement official says authorities are now looking at the person of interest's recent movements.

Police place bullet casing markers outside of a Hilton Hotel in Midtown Manhattan where United Healthcare CEO Brian Thompson was fatally shot (Spencer Platt/Getty Images)

Thompson's family released a statement reading: "Brian was an incredibly loving, generous, talented man who truly lived life to the fullest and touched so many lives."

If you have experienced a bereavement and would like to speak with someone in confidence, contact The Compassionate Friends on (877) 969-0010.