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LONDON (CBSMiami) – Nearly two dozen people were killed, 59 others injured following an explosion at an Ariana Grande concert at the Manchester Arena.

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The explosion went off just as the last song was being performed and the crowd was beginning to exit the arena.

“We now know that a single terrorist detonated his improvised explosive device near one of the exits of the venue, deliberately choosing the time and place to cause maximum carnage, and to kill and injure indiscriminately,” said Prime Minister Theresa May. “The explosion coincided with the conclusion of a pop concert which was attended by many young families and groups of children.”

Greater Manchester police are treating it as a terrorist incident until they know otherwise. ISIS has claimed responsibility for the attack in a brief, generic statement that appeared to get some of the facts of the attack wrong. The U.S. Director of National Intelligence Dan Coats said Tuesday that they had not confirmed if ISIS was responsible.

“I might mention that ISIS has claimed responsibility for the attack in Manchester although they claim responsibility for virtually every attack. We have not verified yet the connection,” said Coats during a House Intelligence Committee hearing.

The explosion killed the suspected suicide bomber and 22 concert goers including children. The first victim was identified Tuesday as 18-year-old high school student Georgina Callander.

May called the terrorist attack among the worst in Britain.

CBS News sources have confirmed that the attacker was identified as 23-year-old Salman Abedi, who was known to British authorities.

At first concert organizers tried to calm people down but then panic set in triggering a stampede.

“We heard a bang, I just ran for my life,” said Charlotte Pinder.

“All of a sudden we heard a massive bang and people were just running from different directions,” said 12-year-old Zara. “When we got up the stairs the smell of smoke was getting strong.”

Grande, who was not hurt, tweeted out that her heart is broken.

The crowd was made up mostly of teens and their parents who had come from as far away as Scotland to see Grande’s ‘Dangerous Woman Tour. Among the first of the dead to be identified were 18-year-old Georgina Callander and 8-year old Saffie Roussous.

“This was a barbaric attack, deliberately targeting some of the most vulnerable in our society,” said UK Home Secretary Amber Rudd.

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“All acts of terrorism are cowardly acts on innocent people,” said May. “But this attack stands out for its appalling, sickening, cowardice. Deliberately targeting innocent, defenseless children and young people who should have been enjoying one of the most memorable nights of their lives.”

Police are still trying to determine if the attacker had accomplices. Hours after the blast, the Arndale shopping center in South Manchester was evacuated and a 23-year-old was arrested. That arrest was “not currently believed to connected to last night’s attacks,” according to police.

Greater Manchester Police said a 23-year-old man was taken into custody in the southern part of the city on Tuesday, and that arrest did appear to be linked to the bombing.

Across the nation, and across the world, friends of Grande took to Twitter to express their thoughts.

Singer Taylor Swift told her 84 million Twitter followers she’s sending all her love to those affected.

Ariana Grande’s manager sent the following out on Twitter, saying, “Words cannot express our sorrow for the victims and families harmed in this senseless attack.”

It was unclear if Grande’s next schedule show — Thursday in London — would take place.