Igor Sergun / arms-expo.ru

Lt. Gen. Igor Sergun, head of the GRU (military intelligence), reportedly died an "untimely" death at the age of 58 from unknown causes. Sergun, appointed by President Vladimir Putin, would have been central to the "hybrid war" against Ukraine that first involved the occupation and annexation of Crimea, then the invasion of Donbas, reads the article by The Interpreter.

Indeed, the accounts of GRU officers captured or killed on Ukrainian territory testify to the GRU's involvement.

The official who died on December 27, 2015,reportedly of heart attack, was Maj. Gen. Aleksandr Shushukin, deputy chief of staff of Russia's Airborne Division, who was said to have led the occupation of Crimea in February 2014.

The claim of Shushukin's role in Crimea were covered mainly by the Ukrainian and alternative Russian-language media.

His death was confirmed with a condolence notice on the web site of the Army General V.F. Margelov Ryazan Higher Airborne Command Academy, of which he had been a graduate, and reportedly on a YouTube post by the Academy.

But as one of the Russian bloggers later noted, the YouTube post was removed later.

This blogger, as others, also wondered if the recent resignation of Aleksei Chaly, head of the occupation parliament in Crimea, was a coincidence. Sergei Menyailo, governor of Sevastopol, also resigned last month.

Read alsoCrimea's de facto head Aksyonov announces purge of local authoritiesThe notice said Maj. Gen. Shushukin served in Afghanistan and also in operations "to restore Constitutional order" in the North Caucasus and Yugoslavia and did not mention the Crimea.

Stanislav Rechinsky, a journalist for Ukrainska Pravda and advisor to the Ukrainian Interior Ministry wrote on his Facebook page:

"Look at this. The second leader of the Russian invasion of Donbas to kick the bucket within two weeks. Speedy karma, however. Awaiting Girkin and Bezler. With Putin."

"Shushukin was in charge of the Russian airborne troops involved in operations in Crimea. Before that there was an operation in South Ossetia. Isn’t it ironic?" said Rechinsky.

Aleksandr Shushukin / mil.ru

Russian opposition member Vladimir Milov wrote on his Facebook page today (translation by The Interpreter):

"For some reason military leaders who organized the military invasion of Ukraine have gone dying. Young. The second in a row."

Read alsoRFE/RL: Russian military intelligence chief dies unexpectedlyIf Shushukin had in fact led the occupation of Crimea -- and his job position suggests that he would well have been involved -- it is odd that that no medal for this "achievement" or mention in his obituary was made, given that President Vladimir Putin acknowledges the role of the Russian military in the anschluss.

No notice appeared on Kremlin.ru or any other federal site.

One Russian-language conspiracy site said Shushukin "was killed by KGB agents as a witness to Vladimir Putin's war crimes and those of the top Russian military command" and that he "may have taken part in the sale of a Buk to the thugs who used it to destroy MH17"; he's even credited with "coordinating the sending of terrorists with whose help Putin brought down the A321" or the Metrojet flight which crashed in Egypt.

“We are unlikely to find out the truth surrounding these military leaders' death, but no doubt they have taken military secrets with them to the grave,” the authors of the article conclude.