The reporter had been on the scene in the Creggan area of the Northern Irish city as police and rioters clashed in violent attacks. Petrol bombs were hurled, cars torched and shots fired. Ms McKee, who had written previously for publications such as Atlantic, Mosaic Science and BuzzFeed, was covering the bloody fighting.
In a heartbreaking tweet, her friend Matthew Hughes said: “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.”
Ms McKee had tweeted just before her death about the “madness” she was witnessing.
Fellow reporter Leona O’Neill described witnessing her colleagues death as leaving her “sick to the stomach”.
A huge security and police presence remained on the scene and incidents of violence broke out soon after.
Assistant Chief Constable of the Police Service of Northern Ireland 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 enquiry.”
Arlene Foster, leader of the Democratic Unionist Party, described the incident as “heartbreaking” and a “senseless act”.
She added: “Those who brought guns onto our streets in the 70s, 80s and 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.”
The attack was also condemned by Sinn Fein.
The party’s deputy leader Michelle O’Neill asserted: “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 violence is being blamed on dissident republicans, who oppose the peace process.