The Islamic State group's group chats were going crazy in the days after the Crocus City Hall attack.
More than 140 killed, an even higher number injured. If last Friday night's deadly ambush at the venue near Moscow proved anything, it's that while the terrorist cell might be down, it's certainly not out.
"The Islamic State doesn't care about when or where exactly. They just want to blow people up, and make sure there is a lot of graphic images of it," says Antonio Giustozzi, a senior research fellow at London's Royal United Services Institute, who specialises in jihadist groups.
That's not to say the assault on the sold-out rock concert wasn't meticulously planned. But these days, the Islamic State group (IS) orchestrates its attacks very differently to when the operation was at the peak of its powers a decade ago.
"We can see it in the chats. They're really enthusiastic about this attack, for them [IS] it's a morale booster," says an analyst, who wishes to remain anonymous.
A combination of factors could have made Russia a target. Although the country's media is state-run, it's influential and competitive: an enticing prospect for IS, which had in January bombed a memorial in Kerman, Iran killing 94 people and injuring almost 300, but with much less global attention.
Grisly images of the carnage in Russia spread far and fast on the country's popular media, and social media platforms too, like VK and Telegram. The world watched on as well.
It blasted Islamic State Khorasan — the Central Asian arm also known as ISIS-K — into headlines around the world.
Terrorism is notoriously hard for intelligence agencies to combat, but Jenny Mathers, an expert in Russian security affairs and senior lecturer in international politics at Aberystwyth University, says the Kremlin "could have taken it's eye off the ball, too".
That's because significant security and intelligence resources have been diverted to the ongoing invasion of Ukraine, and, the recent presidential election.
"This attack came at a time when there's been so much emphasis on cracking down on anti-war protests and making sure ordinary Russians are very closely policed in terms of their everyday activities," she says.
Then, there's the racial element. Russian authorities have, so far, charged four people from Tajikistan, a Central Asian country and former Soviet state, over the attack. The diaspora from this area is subjected to regular discrimination in Russia.
"There are a lot of people who are from Central Asia who have gone to Russia to work as migrants and there's a lot of racism in Russia," Dr Mathers says.
"This is one suggestion of why Islamic State has been able to recruit people from that population."
Terror 'a recurring issue'
While this latest assault represents the deadliest terror attack on Russian soil in 20 years, the country has been a constant target for different groups over the years.
In 1999, when Vladimir Putin was prime minister, several apartment blocks around the country were bombed, killing more than 300 people.
Although, no-one was ever charged over the blasts, Putin's strong military response increased his political popularity early in his reign. Some evidence suggests the Kremlin could have been behind the attacks.
Five years later, in the town of Beslan, dozens of militants stormed a school, taking more than 1,100 — predominantly child — hostages. By the end of the three-day siege, 334 were dead.
In 2015, an explosive device was detonated on a Russian passenger flight travelling from Egypt to Saint Petersburg. None of the 224 passengers and crew survived the crash.
Those headline-grabbing slaughters are punctuated by multiple, less deadly attacks, usually by radicalised Islamists.
Putin has used such security concerns to position himself as Russia's strongman.
"This seems to be a recurring issue. And in spite of all of the attention, and all of the resources that Putin has given to the security services, it's one area they really do seem to be struggling to try and get on top of," Dr Mathers says.
Once, the perpetrators were predominantly Chechen separatists, spurred by Putin's military interventions in the largely Muslim caucus territory.
But the Russian president's support for Bashar Al-Assad's regime in Syria enraged Islamic State, which, during its 2015 heyday, was engaged in ferocious battles with the dictator's forces and controlled swathes of the country's east.
While Putin this week acknowledged "radical Islamists" were responsible for the Crocus City Hall attack, he has also tried to link it to Ukraine. That's something experts don't believe people will buy, at home or abroad.
Mr Giustozzi points out Kyiv has little to gain by masterminding an attack on Russian concertgoers.
"The point is slaughtering civilians with gusto, where there is no plausible military dimension to the target, that is very Islamic State," he says.
IS leaders now 'hiding in basements'
IS once ruled over an estimated 12 million people in Syria and Iraq, and counted numerous cells around the globe among its number. But now it's a shadow of its former self.
By 2019, US, Iraqi and Kurdish forces had recaptured all of the territory the Islamist group held. Its dreams of conquering the world were over.
"The organisation has suffered from that. Years ago, Islamic State would have an extensive terrorist bureaucracy, with a lot of management capacity," Mr Giustozzi says.
The organisation was on life support, but not dead.
At its peak, IS would have orchestrated the Crocus City Hall attack from its strongholds in Syria, Iraq and Afghanistan, where Jihadis would have travelled to train.
"But now, Islamic State's leaders are hiding in basements, in holes and caves in Syria, so they have subcontracted all of this co-ordination to other branches," Mr Giustozzi says.
Pulling all the strings from thousands of kilometres away is no longer viable. And that's where Islamic State's Khorasan branch comes in.
"IS leaders in the Middle East have basically told Khorasan: you handle this. But they do send the cells around the world money, and once they've got that, they can then train locally, get weapons on the black market, and prepare," Mr Giustozzi says.
"The more communication comes from afar, the more there is to intercept, so it's not realistic to expect a message to come from Islamic State leaders in Syria or Afghanistan that says, strike this target at this time near Moscow."
And some communication was intercepted, according to the US at least, which earlier this month issued a warning through its Moscow embassy to avoid large gatherings, including concerts.
Helpful information, on the face of it. But in the Kremlin, the intelligence could have had a different impact.
"There isn't any trust left, I wouldn't have thought, between Moscow and Washington these days," Dr Mathers says.
"In a perverse way, the fact that you get a warning from the country that you regard as a major enemy — one who thinks differently, has different values, different aspirations, you see as a challenger in the world — did they [Russian officials] take it seriously enough to the right people?"
