The word right now on social media is that Ariana Grande, the performer, is okay. Many others are not.

NBC News: Law enforcement officials say at least 20 dead and hundreds have been injured following reports of an explosion in Manchester, UK.

— Tom Winter (@Tom_Winter) May 22, 2017

Most outlets are reporting at least one explosion. The Daily Mail says there were two. The scene inside the arena:

https://twitter.com/hannawwh/status/866775833553379328

Terrorism is obviously suspected, although the explosion(s) supposedly came near the end of the concert — in fact, after the concert was supposed to have ended. Why would terrorists wait that long to set off a bomb? The longer they waited, the greater the chance their plot would have been foiled and/or that the concert would have ended with everyone leaving before the detonation. Strange.

Stand by for updates, needless to say.

Update: Eyewitnesses suggest there was only one bang.

Update: How many casualties were caused by the explosion and how many by the ensuing stampede? Ed emails to say he’s seen reports saying that some people were trampled.

Update: A woman who was there says the concert had just ended and people were on their way out when the explosion occurred. No flash, no smoke. Just a huge bang — one, not two.

Lots of unsupervised kids were there, she says. Imagine.

Witness at Manchester Arena describes scenes of "chaos" as people rushed to leave after "huge bang" https://t.co/Iz9PCxvlJr pic.twitter.com/i2YMBRldJK

— BBC Breaking News (@BBCBreaking) May 22, 2017

Update: Here’s the report of a stampede.

Update: NBC is the only outlet reporting as many as 20 people killed but the BBC now says early estimates put the death toll in “double figures.” The local hospital reportedly is dealing with “mass casualties.”

Assuming it’s a bomb, how’d the bomber get the device into the arena?

Update: Sheer terror.

terrible. https://t.co/kD6DKIEJhs #manchester

— ¡El Sooopèrr! ن c137 (@SooperMexican) May 22, 2017

Update: Ah, this might explain the strange timing of the explosion and why the eyewitnesses in the clip above didn’t see smoke or fire.

https://twitter.com/justinjm1/status/866799010346147840

Sounds like it didn’t inside the concert hall. Maybe the bomber concluded he couldn’t get the bomb past security so he decided to wait in the foyer until the concert ended, as people were filing past him on their way out, before detonating.

Update: As all expected:

U.K. authorities suspect the incident was conducted by a suicide bomber, according to multiple U.S. officials briefed on the investigation…

Multiple senior U.S. intelligence officials who are monitoring British authorities told NBC News that preliminary reports indicate that a single explosion took place outside the arena on the southwest side opposite the train station. The explosion occurred as the concert ended, catching people as they exited.

U.S. officials said initial reports from the scene indicated that a number of the casualties might have been caused by a stampede of concert-goers.

Grande’s audience being what it is, there are likely to be a higher than usual number of children among the dead. Especially girls.

Update: Atrocious. Local PD confirms 19 people dead, for now.

Latest statement on incident at Manchester Arena pic.twitter.com/BEpLOan3dY

— Greater Manchester Police (@gmpolice) May 23, 2017

Update: Worse and worse.

BREAKING: Sources from Manchester hospitals say they're receiving patients with injuries compatible with a nail bomb pic.twitter.com/HEQnZDbTkY

— Rob S (@RobPulseNews) May 23, 2017

Update: Another report of two explosions, this time from CBS:

CBS News confirms there were two explosions at the Ariana Grande concert in Manchester, Englad – the devices contained nails.

— David Begnaud (@DavidBegnaud) May 23, 2017

I haven’t seen a single eyewitness account of two bangs. If there were two, did the bombs go off simultaneously?

Update: No surprises.

CBS News confirms a large group of young girls are among the 19 dead following alleged terror attack at Ariana Grande concert in England

— David Begnaud (@DavidBegnaud) May 23, 2017

Update: Ah, here we go. A firsthand account of two booms:

“The lights came on after the gig and people were starting to leave. As I turned to the left there was an explosion. It was about 40ft behind us near one of the exits. We just thought it was people messing about then it happened again. Another explosion sounded.

“Then we saw the smoke. Everyone just fled. Some people were injured. We saw blood on people when we got outside. People were just running all over the place.

Another eyewitness reports seeing a woman in a wheelchair pushed over as people stampeded to get out.

Update: Why attack a concert instead of some other crowd? Michael Moynihan recalls ISIS’s statement after the attack on the Bataclan in Paris: “[They also targeted] the Bataclan Conference Center, where hundreds of apostates had gathered in a profligate prostitution party…”