On Sunday, between 44,000 and 50,000 Muscovites marched in the Russian capital city to protest the murder of opposition leader Boris Nemtsov who was shot to death on Friday in one of the most secure areas of the city.

The 55-year-old Nemtsov, a figure who represented Russia’s liberal opposition for nearly 20 years, was gunned down just yards away from the Kremlin. “The killing came just hours after a radio interview in which he called on Moscow residents to join an opposition rally on Sunday to protest Putin’s handling of the economic crisis and his ‘mad, aggressive and deadly policy of war against Ukraine,’” the Associated Press reported.

That rally was quickly canceled and replaced with today’s display of mourning. Perhaps recognizing the incendiary nature of Nemtsov’s killing, Moscow quickly granted permission to the new rally’s organizers.

Russian authorities have pledged to thoroughly investigate the incident, but few expect the pursuit of justice in this case to be fair and thorough. When Putin critics have faced premature death in a similar fashion in the past, the investigations into their deaths often serve as opportunities for authorities to impugn the character of the deceased and call into question their associations. Many expect that lamentable history to repeat itself when Nemtsov’s murder becomes the subject of investigation.

Already, Russian officials have offered a series of dubious and paranoid explanations for Nemtsov’s slaying. Of course, the leading suspect at this time is the United States.

“Officially, members of Russia’s Investigative Committee and other top authorities have abstained from specific accusations, saying only that Nemtsov could have been a “sacrificial victim for those who will stop at nothing to achieve their political aims,” Radio Free Europe/Radio Liberty reported. “Many Russians appear to interpret this vague blanket definition as a reference to the United States. The Kremlin has repeatedly accused Washington of organizing last year’s Euromaidan protests and government overthrow in Ukraine and seeking to do the same in Russia.”

An informal online poll by the AntiMaidan organization found that 45 percent of respondents said the United States had arranged the killing of the liberal Nemtsov in order to provoke Maidan-style protests in Russia. (The Russian opposition came in second for essentially the same reason: 23 percent of respondents suggested the opposition was willing to kill one of its own in order to ignite protests.)

Chechen leader Ramzan Kadyrov followed suit, writing on Instagram, “there is no doubt that the murder of Nemtsov was organized by Western intelligence agencies who seek by any means to create internal conflict in Russia.”

(Nonstate media, including Novaya Gazeta, have suggested that Nemtsov was under threat from Kadyrov’s own security personnel for his repeated criticism of the Chechen leader.)

But the USA is not the only culprit believed to be behind this nefarious attack on a beloved Russian political figure. Other pro-Kremlin elements have accused Ukrainian nationalists, Islamic extremists, and even his jealous and jilted Ukrainian girlfriend of plotting to murder this man who was once a leading contender to succeed Boris Yeltsin as the Russian Federation president.

None of these explanations seemed to resonate with the tens of thousands who trudged somberly along the walls of the Kremlin on Sunday. There, many chanted “Russia without Putin” and held signs expressing their outrage with Russia’s presidential administration. Those with the most inflammatory slogans on signs were, however, carted off by police.