The senior detective leading the murder investigation of journalist Lyra McKee has called on the Creggan community to help identify her killer.
Police have published CCTV footage from the attack in the hope that someone recognises the suspected gunman.
Detective Superintendent Jason Murphy said: "Lyra's death is senseless and appalling beyond belief."
He continued: "We know that the people of Creggan do not support what happened and they stand with us today in outrage and disgust at the mayhem that took place on their streets last night."
Police say that they have received a large number of calls from the public already.
They have also stressed that any footage shared on social media, is instead uploaded to their Major Incident Public Portal.
DS Murphy added: "People saw the gunman and people saw those who goaded young people out onto the streets, people know who they are.
"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."
- WATCH: Police release CCTV footage of Lyra McKee's suspected killer