Minutes after a meeting in Moscow with Defense Ministry officials, Yevgeny Prigozhin reportedly boarded his business jet for a quick flight Wednesday afternoon to St. Petersburg. Ten minutes into the flight, when the jet was five miles high, villagers on the ground in Kuzhenkino, Tver Region, heard two booms of an anti-aircraft cannon.

A second business jet did a U-turn and raced back to Moscow. One cellphone video shows Prigozhin’s jet streaming what looks like smoke and spiraling toward the ground. Other videos show it burning in a field. The flight manifest listed as passengers Prigozhin and his right-hand man Dmitry Utkin.

Two months ago, on June 24, the two men spearheaded the biggest challenge in a generation to the rule of President Putin. In an armed mutiny, a motorcade of their Wagner mercenary group took over two cities, and drove halfway up Russia, stopping 125 miles short of the Kremlin walls.

In mourning Wednesday night, Gray Zone, a Telegram channel linked to Wagner, pronounced Prigozhin dead and declared him a hero and a patriot who died at the hands of  “traitors to Russia.”

In signs that Mr. Putin is conducting a wider purge, two Russian news outlets reported today that Russia has removed as head of the air force Sergei Surovikin, nicknamed “General Armageddon.”

A recipient of Russia’s top military award, General Surovikin had directed Russia’s military operation in Ukraine. Seen as an ally of the mercenary leader, though, General Surovikin vanished from public view after the Wagner mutiny.

Prigozhin’s spectacular end seems to send a message — internally and externally. “This is a very clear signal that anyone who challenges the supreme leader does not have a long life ahead of him,” a former CIA Russia analyst, Paul A. Goble, tells The New York Sun. “The fact that Putin does things so openly is the core of his government… Putin believes he benefits by being seen as someone who doesn’t play by the rules.”

The shootdown came in the midst of an annual meeting that Mr. Putin cares deeply about — the reunion of the Brics, or Brazil, Russia, India, China and South Africa. Mr. Putin is not attending the meeting in South Africa, due to an  arrest warrant issued for him in March by the International Criminal Court, accusing the Russian president of war crimes in Ukraine.

“Extraordinary that this happened amid the Brics summit,” London-based analyst Timothy Ash emailed his clients. “A public execution of Prigozhin signals to Russia and the world that a) Putin is still in charge; b) he will go to any lengths to stay in power and those who cross him will be killed.”

Earlier in the day, Putin had suffered another humiliation. India landed its spacecraft on the south pole of the moon. In South Africa, at the Brics summit, Prime Minister Modi waved the Indian flag as he watched the successful lunar landing. 

Russia had been racing India, seeking to make its first lunar landing since the last Soviet one 47 years ago. On Saturday, though, the Russian craft crashed on the moon’s south pole.

Reduced to speaking to the Brics summit by video link, Mr. Putin defended his invasion of Ukraine as a preemptive strike against an imperialist land grab by the West. 

“Our actions in Ukraine are dictated by only one thing — to end the war that was unleashed by the West and its satellites against the people who live in the Donbas,” Mr. Putin said, referring to the eastern part of Ukraine where Russia has been fighting the Ukrainian army since 2014. 

“It was the desire to maintain their hegemony in the world, the desire of some countries to maintain this hegemony that led to the severe crisis in Ukraine.”

On the war front, the news has not been good for Mr. Putin. In recent days, President Zelensky toured Western Europe and thanked Denmark and the Netherlands for their pledges to send a combined total of up to 60 F-16s to Ukraine. Greece, a country sometimes seen as sympathetic to Russia, is to help train the Ukrainian pilots.

In a more symbolic blow, Russia said Wednesday that its forces had downed five Ukrainian drones. Yet one of the drones hit Moscow City, a prestigious business center that was hit twice earlier this month. On Friday, a drone hit Moscow’s Expo Center, a steel and glass office complex that was a base to many Western business investors who ventured into the Soviet Union in the 1980s.

In a minor humiliation, Ukraine’s GUR military intelligence confirmed Wednesday a report by a Russian military blogger that Ukraine had tricked a Russian Mi-8 helicopter pilot into landing at a Ukrainian airfield. The helicopter is being prepared for use by Ukraine’s army.

All this was dwarfed, though, by the demise of Prigozhin, a mercenary who turned on his master. With the list lengthening of Putin opponents who pay “the window tax” — falling to their doom — the death of Prigozhin was no surprise. “Prigozhin was [a] dead man walking as soon as he [stopped] the Wagner march on Moscow,” wrote Mr. Ash, who is senior sovereign strategist at Bluebay Asset Management.

Last month at the Aspen Security Forum, the director of the American Central Intelligence Agency, William Burns, said: “I think Putin is someone who generally thinks that revenge is a dish best served cold.” Mr. Burns, who served as America’s ambassador to Russia betwen 2005 and 2008, added. “If I were Prigozhin, I wouldn’t fire my food taster.”