At least 19 people were killed and 50 more were injured by an explosion outside Ariana Grande’s concert at Manchester Arena tonight. British police are treating the tragedy as an unconfirmed “terrorist incident,” and NBC News is reporting it as a suspected suicide bombing.

TMZ reports that Ariana Grande is physically unharmed but “in hysterics” after the attack, which occurred as her performance ended at around 10:35PM local time, catching concertgoers as they exited the arena. Her next show, scheduled for Thursday at London’s O2 Arena, may be cancelled, both for safety reasons and because Grande is reportedly “in no condition to perform.”

“We are deeply saddened by this senseless tragedy and our hearts and thoughts are with those impacted by this devastating incident,” Live Nation, the concert’s promoter, said in a statement. Prime Minister Theresa May has also issued a statement, saying, “We are working to establish the full details of what is being treated by the police as an appalling terrorist attack. All our thoughts are with the victims and the families of those who have been affected.”

My thoughts, prayers and tears for all those affected by the Manchester tragedy tonight. I'm sending all my love.

— Taylor Swift (@taylorswift13) May 23, 2017

every musician feels sick & responsible tonight—shows should be safe for you. truly a worst nightmare. sending love to manchester & ari

— Lorde (@lorde) May 23, 2017

My heart hurts for my sister, Ariana & every family affected by this tragic event in the U.K. Innocent lives lost. I'm so sorry to hear this

— NICKI MINAJ (@NICKIMINAJ) May 23, 2017

Praying for everyone at @ArianaGrande's show

— KATY PERRY (@katyperry) May 22, 2017

No words can describe how I feel about what happened in Manchester. I don't wanna believe that the world we live in could be so cruel.

— Bruno Mars (@BrunoMars) May 23, 2017