MANCHESTER, England -- For a crowd of mostly young British music fans, the Ariana Grande concert was supposed to be a school night out enjoying cheerful high-energy pop.

It quickly turned into sheer terror instead.

A suicide bomber detonated a powerful explosive device moments after the American singer wrapped up her show Monday night in Manchester, sending people into a desperate search for missing family and friends. The blast killed 22 people and wounded 59 others, with 12 of the wounded under the age of 16, officials said.

The youngest fatality identified so far, Saffie Roussos, was only eight.

In attacking the concert, the bomber targeted an audience full of teenagers and 'tweens -- Grande fans who call themselves "Arianators." Some wore kitten ears, like the star of the show.

Witness spoke of metal nuts and bolts strewn across the blast site, suggesting the explosive was packed with shrapnel.

Fans, many clutching pink plastic balloons, scrambled in panic for exits of the 21,000-capacity Manchester Arena. Some half-climbed, half-tumbled over barriers in terror. Parents waiting outside to pick up their children waded into the fleeing crowds desperately hunting for loved ones.

"It was carnage. Everyone was scrambling over each other ... It was just a race to get out really," said 14-year-old Charlotte Fairclough, who got tickets as a Christmas present.

"We just heard a bang. Everyone stopped and turned around," she said. "You could hear adults telling the little ones it was only a balloon."

Many people took to social media and the hashtag .MissingInManchester became a cry for assistance on Twitter.

"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," tearful mother Charlotte Campbell told ITV television's Good Morning Britain breakfast show.

Her 15-year-old daughter Olivia attended the show with a friend who was found and is being treated in a hospital.

"She's not turned up," Campbell said. "We can't get through to her."

In targeting Manchester, the attacker also struck at one of Britain's cultural hearts. The once-gritty industrial city, along with London and Liverpool, has been one of the main cultural influences on modern Britain, with its iconic Manchester United soccer team, its cross-city rival Manchester City and chart-toppers Oasis, The Smiths and other famous bands. Oasis singer Liam Gallagher tweeted that he is "in total shock and absolutely devastated."

Former Manchester United soccer star David Beckham posted on Facebook: "As a father & a human what has happened truly saddens me. My thoughts are with all of those that have been affected by this tragedy."

Hayley Lunt took her 10-year-old daughter Abigail to the show, her first concert.

"Then we just heard lots of people screaming, and we just ran," she said. "What should have been a superb evening is now just horrible."

"Everyone ran back up the stairs and we eventually got out and they told us to run. We ran out of the arena and there were bodies on the floor," said 21-year-old Bethany Keeling from Keighley in northern England. "It was terrifying."

Grande was physically unhurt but described herself as "broken."

"From the bottom of my heart, I am so, so sorry. I don't have words," she said on Twitter.

Ryan Molloy, 25, said he was just leaving the concert when "there was this massive bang."

"Everyone just went really quiet. And that's when the screaming started," he said. "There were just people all over the floor covered in blood. My partner was helping to try to stem the blood from this one person ... they were pouring blood from their leg. It was just awful."

Andy Holey, who went to pick up his family, said the blast threw him 30 feet (nine meters) through a set of doors.

"When I got up and looked around, there was about 30 people scattered everywhere. Some of them looked dead," he said.

Elena Semino and her husband were waiting by the arena ticket office for her daughter when the bomb exploded. Despite wounds to her neck and a leg, Semino dashed into the auditorium to search for 17-year-old Natalie while her husband, who had only a minor injury, stayed behind to help another wounded woman. She found Natalie and her friends safe.

Manchester residents came together in response to the bombing, offering free rides, food, accommodation and other help to those stranded after the attack.

"I have a sofa, floor, blankets and tea, 5 minutes from Arena for anyone in need," wrote one user on Twitter.

John Leicester reported from Paris