The Islamic State claimed responsibility Tuesday for the attack at a Manchester, England, concert that killed at least 22 people and injured dozens more.
"One of the soldiers of the caliphate placed explosive devices in a gathering of crusaders in the middle of the British city of Manchester," a statement by a suspected Islamic State member read on the encrypted messaging app, Telegram, according to Time.
Roughly 21,000 people packed into the Manchester arena Monday night where pop singer Ariana Grande performed as part of her world tour.
As the show ended, the lights in the arena came on and thousands of people filed out of the building — many of them children going to meet their parents. That's when a suicide bomber detonated his explosive just outside the arena, killing at least 22 people, including an 8-year-old girl, the BBC reported. Another 59 people were injured.
British Prime Minister Theresa May called the attack "the worst attack the city [of Manchester] has experienced," according to Time.
ISIS sympathizers intially celebrated the attack on social media. In one Twitter video, an English-speaking man wearing a mask held up a sign that read "Manchester 2017-05-22," which was the date of the attack.
"This is only the beginning. The lions of Islamic State ... are beginning to attack all the crusaders," the English-speaking man said.
The Telegraph pointed out that other ISIS sympathizers on social media said the attack came in response to the United Kingdom's involvement in the bombing of terror targets in Syria.
SCREENSHOTS Growing celebrations of situation in #Manchester on key Islamic State-linked Telegram channels. Strong… https://t.co/wZcoB9YQHB— Michael S. Smith II (@Michael S. Smith II) 1495498306.0
Police in Manchester launched an investigation to determine whether the attacker, who died in the blast, had help from anyone else.
Dashcam video from one vehicle shows the moment the bomb exploded. The video below shows a faint flash on the left side of the screen.
Moments later, an explosion sounds. The man in the vehicle then shouts "No!" in horror after seeing what happened.
Grande had just exited the stage at the time of the explosion. Hours later, the pop singer took to Twitter to express her condolences.
"[B]roken. from the bottom of my heart, i am so so sorry. i don't have words," the singer tweeted just a few hours after the massacre.
broken. from the bottom of my heart, i am so so sorry. i don't have words.— Ariana Grande (@Ariana Grande) 1495507886.0