By Lauren Mascarenhas and Annette Choi, CNN
Two photos released by NYPD show the unidentified shooter of UnitedHealthcare CEO Brian Thompson Photo: NYPD via CNN
A manhunt is underway for the man who fatally shot UnitedHealthcare CEO Brian Thompson Wednesday morning, in what police believe was a targeted attack.
The gunman shot Thompson outside a hotel in Midtown Manhattan before fleeing through the city.
Police are using video surveillance to piece together the suspect's movements before and after the shooting Wednesday. Here's a visual timeline of the alleged gunman's movements before, during and after the shooting:
Brian Thompson was the CEO of the largest US health insurer, UnitedHealthcare. Photo: LinkedIn / Supplied
Key moments so far
6.15am - Wednesday, 4 December
A surveillance camera image appears to show the suspect in the United Healthcare CEO's murder leaving the 57th Street F train station before the shooting. The image was recorded at 6.15am
Investigators believe that the suspect may have taken a subway from the Upper West Side to Midtown.
6.17am
Video at a nearby Starbucks shows the assailant buying a bottle of water and two energy bars roughly 30 minutes before the shooting, according to police.
6.30am
Around 6:30am, surveillance video captured what appears to be the gunman on the phone.
6.44am
Thompson walked toward the Hilton after leaving his hotel across the street, police said.
The masked gunman was "lying in wait" outside the Hilton Midtown as Thompson made his way to the hotel to attend his company's annual investor conference, according to New York Police Commissioner Jessica Tisch.
The gunman came up behind Thompson and shot him in the back, NYPD Chief of Detectives Joe Kenny said. He then walked toward Thompson and continued to shoot, stopping to clear a gun jam before firing again, Kenny said.
Photo: NYPD
Investigators told CNN that after the shooting, the assailant crossed the street from the Hilton, fled northbound through an alleyway between 54th Street and 55th Street, and got on an electric bike on 55th Street before heading north on 6th Avenue toward Central Park.
6.46am
Patrol officers from Midtown North Precinct responded to a 911 call of a person shot in front of the Hilton Hotel on the avenue of the Americas, between West 53rd Street and West 54th Street, police said.
6.48am
Officers arrived and found Thompson on the sidewalk in front of the hotel with gunshot wounds to his back and leg. He was taken to the hospital by EMS.
NYPD release photos of suspected gunman without mask Photo: NYPD
6.48am
The suspect was seen riding an electric bike in Central Park. This is the last-known sighting of the suspect, according to police.
7am
Video shows what appears to be the suspect on W 85th street. Law enforcement tells CNN that they have seen the video and think it likely shows the gunman.''
7.12am
Thompson was pronounced dead at the hospital, according to police.
11.20am - Thursday, 5 December
The NYPD released images taken at a hostel of an unmasked person of interest wanted for questioning in relation to the shooting. Officials have performed extensive video canvassing, leading them to the hostel in Upper Manhattan, a police official told CNN.
Employees told CNN they remembered a man at the hostel who wore hooded jacket identical to the shooter's and who almost never lowered his mask or hood.
-CNN