British police said Tuesday they have arrested a 23-year-old man in connection with the massacre at an Ariana Grande concert in Manchester, as Prime Minister Theresa May said that authorities know the identity of the suicide bomber who killed at least 22 people at the show.

“With regards to last night’s incident at the Manchester Arena, we can confirm we have arrested a 23-year-old man in South Manchester,” Greater Manchester Police said on Twitter.

May said security officials were not ready to release the identity of the attacker, who detonated the explosive device on Monday night near one of the exits to the Manchester Arena, where singer Grande had just finished performing. In addition to the dead, who included children, 59 people were reported injured.

“All acts of terrorism are cowardly attacks on innocent people but this attacks 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,” she said.

“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.”

Queen Elizabeth II condemned the attack as an “act of barbarity,” voicing sympathy for victims and emergency workers.

“The whole nation has been shocked by the death and injury in Manchester,” the queen said in a statement, Agence France-Presse reported. “I would like to express my admiration for the way the people of Manchester have responded, with humanity and compassion, to this act of barbarity.”

The threat level in the country remained “high,” she noted, meaning a terrorist attack was highly likely, The Guardian reported.

Ambulances carried the 59 wounded to eight hospitals across Manchester and helped 60 “walking wounded.”

“No matter how much we train our staff for incidents such as this, nothing can prepare you for the shock and sadness when tragedies like this occur,” said hospital services chief Derek Cartwright. “This is, indeed, a very sad time for Manchester.”

Meanwhile, frantic family members and friends posted heart-wrenching messages and pictures on social media in the search for their loved ones on Tuesday.

“STILL MISSING: Saffie Rose Roussos, 8yrs old. Missing from Manchester attack,” Adam J. Brown posted on Facebook, next to a picture of her smiling face, Reuters reported.

“White Ariana tshirt-denim skirt-black leggings-black boots.”

“Please…please retweet. Looking for my daughter and her friend,” Michael MacIntyre tweeted along with an image of his daughter Laura and friend Eilidh.

Many parents were waiting for their kids near the arena when the blast sent young fans fleeing for their lives Monday evening.

While many teens found their friends and relatives in the mayhem, some were helped to safety by bystanders, others were offered free cab rides home and dozens were taken to nearby hotels.

A heartbroken Grande said on Twitter: “broken. from the bottom of my heart, i am so so sorry. I don’t have words.”

Paula Robinson, 48, was at the nearby train station with her husband when she felt the explosion and saw dozens of girls screaming and running away from the arena.

“We ran out,” she told Reuters. “It was literally seconds after the explosion. I got the teens to run with me.”

Robinson said she took dozens of girls to the nearby Holiday Inn Express and tweeted out her phone number to worried parents telling them to meet her there.

She said her phone had not stopped ringing since her message.

“Parents were frantic running about trying to get to their children. There were lots of children at Holiday Inn.”

In the hours after the blast, photo montages of smiling faces were circulated of missing teens. They carried the hashtag: “#PrayForManchester.”