Lyra McKee, a 29-year-old journalist has died after shots were fired in Londonderry, with police in Northern Ireland treating the death as a “terrorist incident”.
Police said they believe dissident republicans were behind the night of disorder in the Creggan area blaming the new IRA.
In an early morning press conference Assistant Chief Constable Mark Hamilton said police had information of planned attacks in the city over the Easter weekend and had carried out searches for munitions and firearms.
Lyra had been standing close to a police Land Rover at the time of the shooting.
Mr Hamilton offered his sympathies to the family of Ms McKee and appealed for anyone with information to contact his officers.
He said her death was "horrendous and unjustified".
"Bullets have to stop somewhere and on this occasion, they stopped fatally," he said.
Police said 50 petrol bombs were thrown at police before the gunman appeared at around 11pm. She was rushed to hospital where she died.
ACC Hamilton passed his "deepest sympathies to the family".
"Not only is it a murder of a young woman, it is an attack on this city.
"It will have horrendous consequences which will go on for many, many years."
The police officer appealed for calm.
"These acts of violence bring nothing to the city," he said.
Mr Hamilton said police did not return fire or use any force during the disturbances.
"Police were measured... they saw quite a bit of violence," he added.
Journalist Leona O’Neill said she was at the scene of the killing. She said there was children and teenagers milling about in the area when the gunman appeared and "indiscriminately fire up the street".
He said he did not think Ms McKee was at the scene in a professional capacity but she was entitled to be there on.
"Why she was here is irrelevant, she should not be dead.. she was an innocent bystander."
He said the murder "demonstrates all too starkly when terrorists bring violence and guns into the community members of the public are placed in severe danger".
Alliance leader Naomi Long said:“Devastating news. Thoughts are with Lyra's family and friends. At times like this, words fail. My heart is sore. Those who brought violence and death to our streets have nothing else to offer but more of the same. If you can assist the police, please, come forward. Stop this.”
Petrol bombs were thrown and images from the scene show vehicles alight and others burnt out, with dissident republican terrorists suspected of being behind the attack.
Footage purporting to be from the scene shows at least two shots being fired before a distant scream can be heard.
Assistant chief constable Mark Hamilton, from the Police Service of Northern Ireland, said a murder inquiry had been launched after the death.
He said: “Sadly I can confirm that following shots being fired tonight in Creggan, a 29-year-old woman has been killed.
“We are treating this as a terrorist incident and we have launched a murder inquiry.”
Journalist Leona O’Neill said she was at the scene of the killing.
Writing on Twitter, she said: “I was standing beside this young woman when she fell beside a police Land Rover tonight in Creggan #Derry.
“I called an ambulance for her but police put her in the back of their vehicle and rushed her to hospital where she died. Just 29 years old. Sick to my stomach tonight.”
The murder of this young woman is a human tragedy for her family, but it is also an attack on all the people of this community, an attack on our peace process and an attack on the Good Friday AgreementMichelle O'Neill
The unrest comes ahead of the Easter weekend where republicans mark the anniversary of the 1916 Easter Rising, a time when dissidents are traditionally active.
Politicians have widely condemned the killing.
Sinn Fein deputy leader Michelle O’Neill said the killing in Derry was a “senseless loss of life”.
She said: “I am shocked and saddened at the tragic news that a young woman has been shot dead by so-called dissidents in the Creggan estate tonight.
“The murder of this young woman is a human tragedy for her family, but it is also an attack on all the people of this community, an attack on our peace process and an attack on the Good Friday Agreement.
“I unreservedly condemn those responsible for killing this young woman.
“We will remain resolute in our opposition to the pointless actions of these people who care nothing for the people of Derry.”
Democratic Unionist Party leader Arlene Foster tweeted: “Heartbreaking news. A senseless act. A family has been torn apart.
“Those who brought guns onto our streets in the 70s, 80s & 90s were wrong. It is equally wrong in 2019.
“No one wants to go back. My thoughts are also with the brave officers who stood in defence of their community.”
Gary Middleton, a DUP former deputy mayor of Derry City Council and current Member of the Legislative Assembly, tweeted: “Disgraceful scenes of violence in the Creggan estate tonight.
“PSNI and members of the public being put in danger by unrepresentative thugs intent on destroying communities.”
UUP leader Robin Swann tweeted: "Devastating news coming out of Londonderry (...), a precious life lost, we can't go back to this nor can we allow others to drag us back."
Mark H Durkan, SDLP MLA for Foyle, said he was left “heartbroken and angry” by the killing.
“Just leaving Creggan, heartbroken and angry at the senseless loss of a young life,” he tweeted.
“Violence (only creates victims, that’s all it ever has done. The thoughts and prayers of our city are with the young woman’s family and friends, may she rest in peace.”