The gunman was aiming at police during disturbances in the Creggan when he hit the 29-year-old.Her killing has been widely condemned across the political spectrum.Lyra’s friend Sinead Quinn, who took part on Monday’s protest, said: “We have used red paint because they have blood on their hands for what has happened.”They have encouraged it, they have moulded these young people into what they are and they are standing behind them handing them guns.”They need to take responsibility today for what has happened.”They have shirked it so far by saying it was an accidental shooting. You don’t shoot accidentally.” “I want to reassure people that you don’t have to commit to anything today. I just need to speak to people to understand what they know.”We can then look at how we capture that information in the best way possible to protect those witnesses and enable me to bring the gunman who killed Lyra McKee to justice.” Friends of murdered journalist Lyra McKee defaced the walls of a dissident republican office in Derry with red paintCredit:PA Police in Northern Ireland today said a 57-year-old woman had been arrested under the Terrorism Act in connection with Miss McKee’s murder.In a short statement, the PSNI did not disclose any further details about the nature of the arrest, only that she had been taken to Musgrave Serious Crime Suite. Two teenage men initially arrested by detectives investigating the murder were later released without charge.The senior detective leading the investigation into the 29-year-old’s murder has revealed that since Miss McKee’s death more than 140 people have contacted police with information.Detective Superintendent Jason Murphy said the investigation to find her killer is continuing at a “rapid pace”. The appeal came after friends of the journalist protested by defacing an office belonging to a dissident republican group by putting red handprints on the walls of its headquarters.A number of Miss McKee’s friends walked to Junior McDaid House, where they used a pot of red paint to place handprints on the side of the office walls.A group of some six men, understood to be members of republican group Saoradh, who are associated with the New IRA, stood outside the building during the protest.PSNI officers were also present and later asked for the names of those involved in the incident.The dissident republican New IRA is being blamed for shooting Miss McKee. She added: “When you put a gun into someone’s hand and they shoot it, that’s murder. Friends of murdered journalist Lyra McKee defaced the walls of a dissident republican office in Derry with red paintCredit:PA The New IRA has admitted responsibility for the murder of journalist Lyra McKee in Londonderry, offering “full and sincere apologies” to her family and friends, as police confirmed a 57-year-old woman had been arrested under the Terrorism Act in connection with the killing.Miss McKee was shot dead during unrest in the Creggan area of Derry on Thursday night.In a statement given to The Irish News using a recognised code word, the New IRA said: “On Thursday night following an incursion on the Creggan by heavily armed British crown forces which provoked rioting, the IRA deployed our volunteers to engage.”We have instructed our volunteers to take the utmost care in future when engaging the enemy, and put in place measures to help ensure this.”In the course of attacking the enemy Lyra McKee was tragically killed while standing beside enemy forces.”The IRA offer our full and sincere apologies to the partner, family and friends of Lyra McKee for her death.” Mr Murphy said: “We’ve had a massive public positive response to the investigation since Thursday evening.”This was an attack on the community. Lyra, tragically, was a random victim and I need the public to continue to support us.”Many witnesses have contacted us to give us information that has been provided to them. More than 140 people have contacted us via our MIPP with messages, including mobile phone footage.”House-to house enquiries are continuing, and all of that is to be welcomed.”He added: “My appeal today to witnesses who haven’t come forward to us is simple. Please, come forward and have a conversation with me. Come and talk to me. The New IRA has admitted responsibility for the murder of the 29 year old journalist Credit:PA “Lyra deserves more and I am so glad there are so many people here today to see and watch these men looking at us.”They are not a representation of republican people in this town.”Those people don’t represent (republicanism). Nobody can advocate shooting into a crowd of people and shooting a 29-year-old woman dead.”People have been afraid to stand up to people like this, we are not afraid.”The group of friends have pledged to do more in Lyra’s memory.”Lyra’s McKee’s name will never be forgotten in this town,” Ms Quinn added.”We have to do it for her.” 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.