Friends and family have turned to social media to search for loved ones after a suicide blast claimed by ISIS killed 22 people at a Monday night concert by American pop singer Ariana Grande in Manchester, U.K.
Many children and other youths were among the dead and the 59 wounded in the attack, according to Prime Minister Theresa May, who condemned the "callous terrorist act."
'We were all trying to flee the arena.' — Majid Khan, concertgoer
"We struggle to comprehend the warped and twisted mind that sees a room packed with young children not as a scene to cherish, but as an opportunity for carnage," May said on Tuesday, after a meeting with the country's top security officials.
Shortly after May spoke, police arrested a 23-year-old man in Manchester in connection with the blast.
Manchester police identified the bomber as Salman Abedi, but did not provide further details.
According to British election rolls, Abedi lived at a house in a southern suburb of Manchester that was raided by police on Tuesday.
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For many, the blast sparked a search for loved ones, both online, in emergency rooms and local hotels that gave shelter to the victims. Parents looked for the children they had accompanied or agreed to pick up, and friends searched for each other after groups were scattered by the blast.
Photos of the missing — including many smiling children and teens — quickly filled Twitter and Facebook, often under the hashtag #MissinginManchester.
One post, accompanied by a photo of a young girl in a sparkly top, read: "11 year old Tia and her mum are missing."
Police are also looking online for help with the investigation, calling on anyone with photos or video from the scene to upload them for review.
Campaigning for Britain's June 8 election has been suspended.
May praised the efforts of emergency personnel and everyone else in the northern city who helped in the aftermath.
Because public transport was shut down, taxis offered free rides home to stranded concertgoers, while residents opened their homes to provide lodging.
"They… embody the spirit of Manchester, a spirit that has never been broken and never will be broken," she said.
The Islamic State in Iraq and Syria (ISIS) has taken responsibility for the attack, claiming in a statement a "soldier of the caliphate" placed a bomb at the arena. If true, it remains unclear whether the bomber was an actual member of the extremist group, or if he was inspired by it.
Some experts discounted the statement, noting there was no evidence of direct involvement and that details of the ISIS claim — in two contradictory postings — contrasted with the British police account.
It's the deadliest attack in the U.K. since 52 people were killed by suicide bombings in London's transport system in 2005.
Police said they raided two residential areas in south Manchester one of which, according to the British election rolls, was the apartment of the suspected bomber.
Officers conducted a controlled explosion to enter the modest red-brick semi-detached house, according to Manchester's chief constable.
Heavily armed and helmeted police were seen coming and going on Tuesday. Plainclothes officers wearing gloves removed bags from the apartment.
Most neighbours said they knew little about the inhabitants of the house, except that several people lived in it.
The leafy residential road is about a kilometre from the supermarket where police made an earlier arrest in connection with the attack.
No details were immediately available about the second raid.
The first of the victims was identified on Tuesday.
Georgina Callander, an 18-year-old student from the town of Leyland, was killed in the attack according to a statement from Runshaw College, where she was studying health and social care.
Callander apparently met Grande two years ago, when the U.S. singer performed at the same arena. They are seen together in photos posted to Callander's Instagram account.
"I am so happy right now," Callander wrote at the time. "Hands down the best concert of my life."
The explosion struck around 10:30 p.m. local time as Grande was ending the concert, part of her Dangerous Woman Tour. Police cars, bomb-disposal units and 60 ambulances raced to the scene as the scale of the carnage became clear. More than 400 officers were deployed.
"A huge bomb-like bang went off that hugely panicked everyone and we were all trying to flee the arena," concert-goer Majid Khan, 22, told Britain's Press Association.
Concertgoer Jess Kelly, 22, said the blast struck as she and a friend were headed to the concession area.
"We heard the explosion, everybody turned to the left, screamed and started running," she told CBC's Carole MacNeil.
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Kelly and her friend went back to the main concert arena to try to get away from the mass of people that were "stampeding out" of the building.
She said they were some of the last people out of the building.
Video from inside the arena showed concertgoers screaming as they made their way out amid a sea of pink balloons.
Grande, who was not injured, tweeted hours later: "broken. from the bottom of my heart, i am so so sorry. i don't have words."
'I've called the hospitals'
The city's regional government and its mayor, Andy Burnham, were among scores of Twitter users who circulated the #MissinginManchester hashtag, used by people looking for family members and friends.
Among the names being circulated was Olivia Campbell. Her mother, Charlotte Campbell, said the 15-year-old attended the concert with her best friend from school. He is hospitalized but Olivia is missing, the mother told ITV television's Good Morning Britain breakfast show.
"I've called the hospitals. I've called all the places, the hotels where people said that children have been taken and I've called the police."
She said she last heard from her daughter just before the concert.
"If anyone sees Olivia, she knows my number."
The Dangerous Woman Tour is the third concert tour by Grande, who rose to fame on the high school sitcom Victorious, and supports her third studio album, Dangerous Woman.
The tour began in Phoenix in February. After Manchester, Grande was to perform at venues in Europe, including Belgium, Poland, Germany, Switzerland and France, with concerts in Latin America and Asia to follow.
Pop concerts and nightclubs have been a terrorism target before. Almost 90 people were killed by gunmen at the Bataclan concert hall in Paris during a performance by Eagles of Death Metal in November 2015.
In Turkey, 39 people died when a gunman attacked New Year's revellers at the Reina nightclub in Istanbul.
Manchester, 260 kilometres northwest of London, was hit by a huge Irish Republican Army bomb in 1996 that levelled a large swath of the city centre. More than 200 people were injured, though no one was killed.
EXPLOSION AT MANCHESTER ARENA AND EVERYONE RAN OUT SO SCARY😭 pic.twitter.com/pJbUBoELtE— @hannawwh