Videos released by police appeared to show the moment a gunman fired the shots which killed journalist Lyra McKee.
Police Service Northern Ireland released mobile phone footage which shows the masked suspect, clad in black, point a gun from behind cover and fire towards police and a crowd of onlookers.
A second suspect, dressed in black with light trainers, is then seen crouching at the same spot and reaching towards the ground.
In separate CCTV footage also released by police, Ms McKee, 29, can be seen among a crowd of people stood by a police vehicle moments before she was shot.
She raised her mobile phone into the air, apparently to take a photo of a violent confrontation between police and a group believed to be dissident republicans.
A third CCTV clip shows the masked shooter head-on, standing yards from a burning vehicle, as he steps from behind a wall then points a handgun towards police and bystanders.
Detective Superintendent Jason Murphy said: “We are issuing CCTV from the incident to encourage anyone with information to make contact with us.”
“We also know that a range of footage is circulating on social media however I cannot stress enough how important it is that people who were in the area last night and who recorded video and took photos share what they have with us via our Major Incident Public Portal,” he added.
“People saw the gunman and people saw those who goaded young people out onto the streets, people know who they are.”
The gunman is only seen to emerge from behind cover for several seconds to aim the handgun. Timestamps show the pieces of footage were recorded between 9.58pm and 10.05pm.
Police have blamed the New IRA for the killing in the Creggan estate on Thursday night.
Please assist our investigation into the murder of Lyra McKee by uploading any footage you have to the Major Incident Public Portal via the following link: https://t.co/EL93YAAEMB … pic.twitter.com/vm7Q6hO4cH
— PSNI (@PoliceServiceNI) April 19, 2019
DS Murphy said: “The answers to what happened last night lie within the community. I am asking people to do the right thing for Lyra McKee, for her family and for the city of Derry/Londonderry and help us stop this madness.”