Police have released CCTV images of Lyra McKee’s final moments as an investigation is launched to trace her killer. The 29-year-old journalist was shot in the head as she reported on the riots in Londonderry on Thursday night and died later in hospital.Detectives have published footage which shows the street around the time of the incident, including what appears to be the murder suspect opening fire. In the video, Miss McKee can be seen in a crowd watching the protest shortly before an unidentified gunman opened fire. Police have circled a CCTV still of the man they believe is the suspect. Detective Superintendent Jason Murphy has made a passionate appeal to the community to encourage those with information to come forward. He said: “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.” Miss McKee’s partner Sara Canning, paid tribute at a vigil for the late reporter: “It has left me without the love of my life, the woman I was planning to grow old with.”Our hopes and dreams and all of her amazing potential was snuffed out by this single barbaric act,” “This cannot stand, Lyra’s death must not be in vain because her life was a shining light in everyone else’s life and her legacy will live on and the life that she has left behind.”Theresa May, the Prime Minister, offered her condolences to Miss McKee’s friends and family after the “shocking and truly senseless” death.”She was a journalist who died doing her job with great courage,” she said. He added that her death was ‘senseless and appalling beyond belief’ and highlighted that it represents the tragic loss of promise and loss of potential. Sinn Fein Leader Mary Lou McDonald (left), DUP leader Arlene Foster (right) with Sara Canning (centre), the partner of 29-year-old journalist Lyra McKee, at a vigil in LondonderryCredit:Brian Lawless/PA Wire Officers believe that they were the gunman’s intended target. The final tweet from Lyra McKee “However it should not be the loss of hope. 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.”Politicians from across the divide came together following the tragedy to call for calm in Northern Ireland.The death of the 29-year-old journalist on what was described as a “dark day” for the country has been met with “global condemnation, horror and revulsion”, police and politicians said. Trouble flared at Creggan, a large housing estate on the outskirts of Derry, at about 9pm on Thursday night as police carried out an intelligence-led raid looking for firearms and explosives they believed were going to be used to attack officers over the weekend. Lyra McKee was shot as republicans targeted police Former US president Bill Clinton tweeted to say he was heartbroken by Miss McKee’s murder and the violence in Londonderry. Mr Clinton added: “The challenges in NI (Northern Ireland) today are real-but we cannot let go of the last 21 years of hard-won peace and progress. This tragedy is a reminder of how much everyone has to lose if we do.” Police are treating it as a terrorist incident and say they believe that the New IRA may be behind the killing.It comes amid fear of rising sectarian violence in the area and calls for calm during the weekend’s commemorations of the 1916 Dublin uprising that led to Irish independence.In a rare move Arlene Foster of the DUP, Sinn Fein’s Michelle O’Neill, Robin Swann of the UUP, Colum Eastwood of the SDLP, Alliance’s Naomi Long and Clare Bailey of the Green party issued a joint statement described the killing as an attack on the peace process.”We are united in rejecting those responsible for this heinous crime,” they said. “This is a time for calm heads.” Police have released a CCTV still of a man suspected of firing the shots that killed Lyra McKeeCredit:PA Assistant Chief Constable Mark Hamilton said. “We believe this to be a terrorist act, we believe it has been carried out by violent dissident republicans, our assessment at this time is that the New IRA are most likely to be the ones behind this and that forms our primary line of inquiry. “Deputy Chief Constable Stephen Martin said they are looking for “more than one person” who they believe were involved in the shooting.He added: “We carried out that search activity last night because we believed that there were people in this city who over this weekend were going to mount murderous attacks on the police and perhaps even other events.”He called for calm over the weekend for those with information to come forward and “make this madness stop”.The New IRA were blamed for a car bomb which exploded outside a court in the city in January and the group has claimed responsibility for a number of parcel bombs sent to London and Glasgow recently.There was backlash after a statement on the website of Saoradh, a political party with links to dissident republicans, said she was killed accidentally during “resistance from the youth” against British forces. Irish Taoiseach Leo Vardakar said his government condemned the violence in the “strongest possible terms”.”Twenty-one years ago today on Good Friday, we as a people, north and south, chose peace, democracy, powersharing and ever closer co-operation, and we will not be dragged into the past.” More than 50 petrol bombs were thrown and two cars were hijacked and set on fire, creating burning barricades.Miss McKee was stood among a crowd which included women and children when a gunman started shooting indiscriminately around a corner, witnesses said.Leona O’Neill, a fellow journalist, said that she took cover after hearing the “pop, pop” of gunfire when she saw Miss McKee lying on the ground.She said: “Her friends had realised what had happened – obviously they put two and two together, the pop of the gunfire and she was lying down on the ground – they started screaming that she had been shot.”They tried to pull her to safety before the police “put her in the back of the Land Rover and drove her at speed with sirens going and the lights going through the burning barricade to the hospital,” Ms O’Neill told the BBC.The attack came just hours after a US politician has praised the Good Friday agreement as a “beacon of hope”. Ms O’Neill noted: “And I am standing in Creggan where the road is strewn with glass and there is a young woman lying dead after being shot. Everyone was shocked. There were people crying in the street, there was a real, real anger about how this could happen.” As well as as working as a freelance journalist Miss McKee had almost finished her second book The Lost Boys.Alison Millar, a documentary maker who had known Miss McKee since she was 15, said that she had been due to have dinner with Miss McKee on Friday evening.She said that her friends and family were in “such shock” at the violence and at the loss of “this incredible women who would have literally given you the shoes off of her feet, the most compassionate human being, the most beautiful genius and talent.”Michelle Stanistreet, NUJ general secretary, said: “A young, vibrant life has been destroyed in a senseless act of violence… “A bright light has been quenched and that plunges all of us in to darkness.” Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.