■ The Islamic State claimed responsibility for a bombing Monday night in the foyer outside the main hall of the Manchester Arena that killed 22 people and wounded 59 others. View photos from the aftermath of the attack.

■ Children and teenagers who were attending a concert by the American pop star Ariana Grande were among the dead, the police said. An 18-year-old student and an 8-year-old girl were confirmed killed in the bombing. Ms. Grande was not hurt.

■ The police say a man detonated an “improvised explosive device” and died at the scene. Investigators say they believe the man acted alone, but they are investigating whether he was part of a wider network.

■ Prime Minister Theresa May described the episode as “an appalling terrorist attack,” and said law enforcement officers believed they knew the identity of the attacker, but were not ready to confirm his name.

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Wounded people inside the Manchester Arena after a bombing at an Ariana Grande concert Monday evening. Credit Press Association, via Associated Press

What We Don’t Yet Know

The police have not released the identity of the bomber, nor have they commented on the motive of the assailant. It is also not clear whether he received help and whether he intended to kill himself.

The Islamic State claimed responsibility for the attack, identifying the bomber in its statement as a “soldier of the caliphate,” but the extent of the militant group’s connection is unclear.

We are also trying to find out:

■ How many of the 22 victims were children.

■ What gaps in security at the arena might have abetted the attack, and what could have been done to prevent it.

■ What effect the attack might have on the June 8 general election. Britain’s leading political parties agreed to suspend campaigning out of respect for the victims of the attack.

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First Victims Are Identified

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Police officers moved flowers left at a makeshift memorial in Manchester. Credit Ben Stansall/Agence France-Presse — Getty Images

Saffie Rose Roussos, an 8-year-old from Lancashire in northwest England, was attending the Ariane Grande concert with her mother and older sister, the Lancashire County Council said on Tuesday. Saffie was killed in the attack. News reports said her mother and her sister, who is in her 20s, were being treated at a hospital for their injuries.

The principal of Tarleton Community Primary School, which Saffie attended, said she was a “beautiful little girl,” who was “quiet and unassuming, with a creative flair.” The principal, Chris Upton, said that news of Saffie’s death had been a “tremendous shock.”

Earlier, Georgina Bethany Callander, an 18-year-old health and social care student, was the first victim of the Manchester attack to be identified on Tuesday. News reports said she had died with her mother at her bedside.

Read more about the victims who have been identified here.

Others in Manchester were still appealing for help locating loved ones who had attended the concert.