The world is reacting in horror and disbelief after an Ariana Grande concert in Manchester, England, ended in bloodshed and chaos Monday night.
Shortly after a suicide bomber detonated explosives as concertgoers exited Manchester Arena, the #MissingInManchester hashtag flooded the internet in a desperate hunt to find those still missing.
Manchester's regional government and its mayor, Andy Burnham, are among scores of Twitter users socializing the hashtag with names and photos to help people find family members and friends who remain unaccounted for after the deadly blast.
Those among the missing is Olivia Campbell, a 15-year-old girl who attended the concert with a friend from school. Her mother, Charlotte Campbell, said on Good Morning Britain that Olivia's friend had been found and is being treated in a hospital. But Olivia is still missing. Campbell said she hasn't heard from her daughter since Olivia called home just before the concert.
"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," Campbell said on the show. "If anyone sees Olivia, lend her your phone, she knows my number."
Many of Grande's fans are young, and British police say that children are among the dead.
Grande, who had just left the stage when the explosion occurred, was unhurt.
An outpouring of support for the victims and their families from across the world has flooded social media over the last several hours.
James Corden, British television host of the Late Late Show, extended his support for the people of Manchester during his show.
"When I think of Manchester, I think of the spirit of the people there," Corden said, "and I'm telling you, a more tight knit group of people you will be hard pressed to find."
President Donald Trump, who is on his first overseas trip, condemned the "evil losers" who carried out the attack.
German Chancellor Angela Merkel says it's "incomprehensible" that someone would target a pop concert to kill and wound people.
Merkel said in a statement that the attack "will only strengthen our determination to keep acting together with our British friends against those who plan and carry out such inhuman deeds. ... I assure people in Britain that Germany stands beside you."
Merkel's spokesman, Steffen Seibert, tweeted: "Our thoughts (and) prayers are with the people in #Manchester affected by the blast. We mourn for the dead (and) hope the injured can recover fully."
Celebrities also offered their support.
Witnesses described the chaotic scene and rush of concertgoers after the explosion as "a stampede."
Andy Holey, who went to the arena to pick up his family, said the blast threw him some 30 feet through a set of doors.
"When I got up and looked around there was about 30 people scattered everywhere, some of them looked dead, they might have been unconscious but there was a lot of fatalities," he said.
"Everyone was screaming and running," Robert Tempkin, 22, told he Times of London. "There were coats and people's phones on the floor. People just dropped everything."
Elena Semino and her husband were waiting by the arena ticket office for her daughter when the explosion went off.
"My husband and I were standing against the wall, luckily, and all of a sudden there was this thing," she told he Guardian. "I can't even describe it. There was this heat on my neck and when I looked up there were bodies everywhere."
Despite wounds to her neck and a leg, Semino dashed into the auditorium in search of her daughter while her husband, who had only a minor injury, stayed behind to help an injured woman. She found her daughter Natalie, 17, and her friends safe.
Questions over the arena's security were also raised in the hours following the blast.
A Czech woman who attended the concert said "there was almost no security check, rather zero. They let us get in without any check if we have anything with us."
Nikola Trochtova told Czech public radio that "the only thing they were interested in was if we had any bottles of water with us. They almost didn't check our bags, they didn't take a look."
Information from The Associated Press was used in this report.