While most of Britain prepared for bed, a suspected terrorist attack struck the city of Manchester Monday night. Details are still thin, but here's what's known so far:
At least 22 people, including children, were killed and 59 were injured, said Ian Hopkins, the chief constable for Greater Manchester Police.
As people were leaving a concert by American pop singer Ariana Grande at the Manchester Arena, loud explosions were heard outside the main area.
Many of Grande's fans are teenage and pre-teen girls (they call themselves the Ariana Army), so there would've likely been a lot of young people in attendance.
The initial reports of an explosion first came in at about 10:33 p.m. local time, according to Manchester police.
Local authorities are encouraging people with concerns or information to report them to an anti-terrorist hotline. They also have an emergency number for those concerned about loved ones -- +44 (0)161 856 9400.
The singer is OK. Her management have released a statement saying "we mourn the lives of children and loved ones taken by this cowardly act."
Grande tweeted: "broken. from the bottom of my heart, i am so so sorry. i don't have words."
Witnesses told CNN they heard one explosion near the arena. The blast occurred in a "public area" outside the venue, the Arena said in a statement.
There haven't been any claims of responsibility, but authorities are investigating if it was a suicide attack. The assailant was carrying an improvised explosive device and died at the scene, Hopkins of the Greater Manchester police said Tuesday morning.
"We believe at this stage that the attack was conducted by one man. The priority is to establish whether he was acting alone or as part of a network," Hopkins said.
After the initial explosion, Manchester police said they conducted a precautionary controlled explosion in nearby Cathedral Gardens to destroy what turned out to be discarded clothing.
Victims and concertgoers
Police said the wounded were sent to six hospitals across Manchester, one of the UK's largest cities.
"After the first wave of sirens and the evacuation, it was filled with cars. The roads were bedlam. People just going through red lights," said Sam Ward, who lives near the arena.
The hashtag #RoomForManchester began trending as a way for locals to offer shelter or transport to those who needed it.
Facebook has activated its "Safety Check" feature.
Images quickly flooded the internet following the blast.
A dashcam caught the explosion from afar.
Other images show the chaotic aftermath.
What's next for Britain
British Prime Minister Theresa May said in a statement that authorities "are working to establish the full details of what is being treated by the police as an appalling terrorist attack."
She will chair a meeting of the government's emergency Cobra committee early Tuesday morning.
All three of the country's leading political parties have suspended campaigning for the upcoming general election on June 8. The Scottish National Party has also postponed or suspended some of their own events.
Amber Rudd, the British Home Secretary, is urging the public to "remain alert, not alarmed."
More than 400 police have been deployed throughout Manchester, said Hopkins, the chief constable. People can expect to see armed officers on patrol throughout the city, he said.
Manchester Mayor Andy Burnham thanked his constituents during a heartfelt news conference Tuesday.
"Even in the minutes after the attack, they opened their doors to strangers and drove them away from danger. They gave the best possible immediate response to those who seek to divide us, and it will be that spirit of Manchester that will prevail and hold us together," he said.
Manchester links to radicalism
The Manchester incident comes nearly two months after an assailant killed five people outside Parliament in London, the first mass-casualty attack since the 2005 London bombings.
Police conducted a series of raids in Manchester -- which is home to a large and well-established Muslim population -- following that attack.
Earlier this year, Jamal Udeen al-Harith, a 50-year-old from Manchester, carried out a suicide bombing in Iraq on behalf of ISIS. While Pakistani national and Manchester resident Abid Naseer was convicted of a plot to bomb the city's central Arndale shopping center in 2015.
The attack also comes on the fourth anniversary of the killing of British solider Lee Rigby.