A journalist was shot dead during riots in Northern Ireland in what police on Friday were treating as a terrorist incident.
"Lyra McKee was murdered during orchestrated violence in Creggan last night," Assistant Chief Constable Mark Hamilton said.
On Friday, the police tweeted CCTV footage of the suspect wanted in connection with her murder.
Detectives investigating the murder of Lyra McKee release CCTV footage and ask people to come forward with information. Call us on 101. https://t.co/Z1GP93HLLl
— Police Derry City and Strabane (@PSNIDCSDistrict) April 19, 2019
McKee had posted an image that appeared to be from the riots in the Creggan housing estate in the city of Derry, also known as Londonderry, accompanied by the words "Derry tonight. Absolute madness."
Images of the unrest posted on social media showed a car and van ablaze and hooded people throwing petrol bombs and fireworks at police vehicles.
"A single gunman fired shots in a residential area of the city and as a result wounded Ms McKee," said Hamilton, adding that police believed the gunman was a "violent dissident republican".
"We are treating this as a terrorist incident and we have launched a murder inquiry," he said.
Journalist Matthew Hughes earlier identified the dead woman as one of his friends.
"I just received the heartbreaking news that my friend @LyraMcKee was murdered tonight in a terrorist incident in Derry," he tweeted.
I just received the heartbreaking news that my friend @LyraMcKee was murdered tonight in a terrorist incident in Derry.
— Matthew Hughes (@matthewhughes) April 19, 2019
She was one of my closest friends. She was my mentor. She was a groomswoman at my wedding. I can't imagine life without her, and yet now I must. I'm devastated
McKee had written for The Atlantic magazine and BuzzFeed News. She was named by Forbes magazine in 2016 as one of their "30 under 30" outstanding figures in media.
Leona O'Neill, a reporter with the Belfast Telegraph, said she saw Ms McKee get hurt.
"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," she tweeted.
Thursday's unrest raised memories of past decades of violence in Northern Ireland.
Ireland's Prime Minister Leo Varadkar warned that "we cannot allow those who want to propagate violence, fear and hate to drag us back to the past".
His British counterpart Theresa May said the killing was "shocking and truly senseless".
In Brussels, a European Commission spokesman condemned the "terrible incident".
"We condemn such violence, and we are confident that the UK authorities will ascertain the exact circumstances of this tragic event," he said.
The violence came in the run-up to the Easter weekend, when Irish republicans opposed to the British presence in Northern Ireland mark the anniversary of a 1916 uprising against British rule.
A car-bombing and the hijacking of two vans in Derry earlier this year were also blamed on a dissident republican paramilitary group.
Michelle O'Neill, the deputy leader of Irish republican party Sinn Fein, condemned the killing.
"My heart goes out to the family of the young woman shot dead by so-called dissidents," she tweeted.
"This was an attack on the community, an attack on the peace process and an attack on the Good Friday Agreement," the peace deal that largely brought an end to violence on the island exactly 21 years ago, she added, calling for calm.
Arlene Foster, leader of the Democratic Unionist Party, which is in favour of Britain's presence in Northern Ireland, described the death as "heartbreaking news".
"A senseless act. A family has been torn apart. Those who brought guns on to our streets in the 70s, 80s & 90s were wrong. It is equally wrong in 2019. No one wants to go back," she tweeted.
The Good Friday Agreement in 1998 largely brought an end to three decades of sectarian bloodshed in Northern Ireland between republican and unionist paramilitaries, as well as British armed forces, in a period known as the Troubles.
About 3,500 people were killed in the conflict - many at the hands of the Irish Republican Army.
Police blamed a group called the New IRA for the flare-up in violence in recent months.
Some expressed fears that recent attacks could be a sign that paramilitaries want to exploit the current political turbulence over Northern Ireland and its border with the Republic of Ireland caused by Brexit.
Derry was the scene of one of the darkest episodes in the Troubles in 1972, known as Bloody Sunday, when British troops opened fire on a civil rights demonstration and killed 13 people. A 14th victim later died of his wounds.
A former British soldier was charged with murder last month over the killings.
