Kremlin opponent Boris Nemtsov's blood was barely dry on the Moscow sidewalk before powerful Russians came up with a startlingly clear conclusion: that the West was to blame.
The West stands accused of an increasing number of outrages in President Vladimir Putin's Russia.
All powerful state television networks, cowed newspapers and a tame parliament mean the Kremlin has no lack of mouthpieces for a campaign to persuade Russians that they are under attack, by a Cold War-style enemy beyond their borders and by what the media regularly calls "traitors" and "fifth columnists" within.
That set the tone for what followed.The investigative committee assigned to Nemtsov's case quickly issued a list of possible motives.
In fact, the top option offered by the authorities was that Russia's beleaguered and poorly supported opposition had itself killed Nemtsov in order to create a scandal.
The Kremlin appointed leader of Chechnya, Ramzan Kadyrov , a man repeatedly accused of overseeing torture and extrajudicial executions, announced "there was no doubt" about Nemtsov's murder.
It "was organised by Western secret services to provoke an internal conflict in Russia," said Kadyrov, one of Putin's most ardent supporters.
The conspiracy theories recalled the reaction to the shooting down of Malaysia Airlines flight MH17 over rebel-controlled eastern Ukraine in July 2014.
One theory even suggested the airliner was shot down because its logo resembled the Russian flag and that Ukrainians thought they were shooting at Putin's presidential jet.
'Information War'
Communist lawmaker Ivan Melnikov drew a specific parallel between Nemtsov and MH17.
"If you look at the timing, all this looks like a bloody provocation organised with the same goal as the downing of the Boeing," he said.
The aim was "to invite unrest in the country and unleash an anti-Russia hysteria abroad," he said.
That was a message repeated by a string of personalities on state news channel Rossiya 24.
"This is an operation in which we can see the hand of the Western secret services," said the former speaker of the Russian parliament's lower house, Gennady Seleznev.
Political analyst Alexei Martynov said: "I would like to draw your attention to the fact that the Americans reacted (to Nemtsov's murder) with suspicious promptness."
A similar pattern of conspiracy theories emerged when Anna Politkovskaya, the crusading journalist who exposed the horrors of Chechnya, was shot dead at the entrance of her home in central Moscow in 2006.
And, as with the deaths of numerous other opposition-minded figures, her killing has never been fully solved.
'Darkest Instincts'
The way the conspiracy theories emerge and take over resembles an organised effort.
Former US ambassador to Moscow Michael McFaul tweeted that he had received "hundreds, if not thousands of tweets" with the same wording: the "USA killed Nemtsov", in what he called an obvious "paid campaign".
But the reaction to Nemtsov's death is only part of a wider web of anti-Western sentiment that the authorities encouraged against Nemtsov and other opposition figures.
State-controlled NTV television had been on the point of broadcasting a new documentary denouncing opposition leaders including Nemtsov, but pulled the show after his murder.
It's not just on the airwaves, either. A big pro-Kremlin rally a week before Nemtsov was killed featured placards reading: "Let's finish off the fifth column."
For some, the atmosphere makes violence inevitable, whoever actually pulled the trigger.
"The murder of Nemtsov is on the conscience of the authorities, which have let loose the darkest instincts of the pogrom," prominent Russian lawyer Genrikh Reznik wrote on Twitter.
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