DONETSK, Ukraine — Bragging on social media about his fighters downing what they thought to be a Ukrainian military transport plane, the self-appointed separatist commander declared: “We did warn you — do not fly in our sky.” A day later, after it had become clear that the aircraft was not a cargo jet transporting government troops but a Boeing 777 carrying 298 passengers, Igor Strelkov claimed in a weird statement that “not all the people on the plane were dead before it crashed,” insinuating that some were.

In a bizarre post on VK.com, the Russian equivalent of Facebook, Strelkov asserted that corpses strewn about the crash scene in the rural eastern Ukrainian village of Grabovo were “bloodless” and insinuated that Kiev may have deliberately shot the plane down as part of some sinister plan. Strelkov claimed that he had spoken to "two people who personally collected the bodies immediately after the crash" and that they had “stressed that many corpses were ‘entirely bloodless’ — as if their blood had clotted long before the accident.”

Furthermore, he wrote, “the plane was discovered with a large quantity of drugs, blood serum and other things, which is not characteristic for a conventional airliner. It seems that there was some sort of special medical cargo." Indeed there was — dozens of passengers aboard the plane were AIDS researchers en route to a global conference. Hence the medical supplies.

Strelkov, a native Muscovite whose real name is Igor Girkin, is a brutal and deranged pro-Russian rebel leader who has emerged as a key figure in eastern Ukraine.

In this Friday, July 11, 2014 file photo, Igor Girkin also known as Igor Strelkov, a pro-Russian commander, center, arrives for the wedding of platoon commander Arsen Pavlov and Elena Kolenkina in the city of Donetsk, eastern Ukraine. Image: Dmitry Lovetsky, File/Associated Press

A self-professed former agent with Russia’s Federal Security Service (FSB) who retired in March 2013, Strelkov fought in several post-Soviet conflicts including Transnistria, Serbia and Chechnya. Ukrainian and Western officials believe he might be an active Russian intelligence officer but have been unable to offer proof. The Security Service of Ukraine, or SBU, has released recordings of what it says is Strelkov taking orders from agents in Moscow, but the recordings have not been independently authenticated. Beyond his brutality, Strelkov is known as a master of what the Russians call “maskirovka” –- disguise and deception. Kiev holds him responsible for the heinous torturing and killing of a local pro-Ukrainian official in Horlivka, a city of some 200,000 north of Donetsk, last May. Witnesses saw gunmen subservient to Strelkov take the official whose body was later found at the bank of a river, along with a second man. Both had their stomachs slashed open. He has also ordered the detention of hundreds of hostages, including OSCE monitors, journalists and activists. And Ukraine’s Interior Minister Arsen Avakov has described him as “a monster and a killer." Soot-stained documents recovered from his former office in the city of Sloviansk, the separatists’ stronghold and until recently the epicenter of the bloody conflict, reveal that Strelkov led illegal trials by “military-field tribunal” in which at least three men were sentenced under a 1941 Stalin-era decree to death by firing squad. In May, Reuters visited the sleepy neighborhood in northern Moscow where Strelkov used to live in a nine-story-building, and where his mother and ex-wife still reside.

A Ukrainian journalist shows a photograph of Igor Strelkov, a military commander of pro-Russian militias in Slovyansk, to his supposed neighbor in Moscow, Russia, Tuesday, April 29, 2014. Image: Ivan Sekretarev/Associated Press

The news agency quoted a neighbor, Galina Ivanovna, whose apartment is two floors below Strelkov’s, as saying she saw him last about six months ago, and that he was always “very polite and very quiet.” “He always wore a tie, would walk to work. Nothing about him was particularly outstanding,” she said. He does seem, however, to be an ardent fan of war. Shortly after he surfaced in eastern Ukraine and installed himself as the defense minister of the self-styled Donetsk People’s Republic, images of him participating in war reenactments spread across the Internet. So did other biographical information, such as the fact the he had published a journal of his combat adventures titled “Bosnian Diary” in 1999, in which he described the thrill he experiences when in battle. “After the first euphoria — we’re alive! — came the sensation familiar to most professional fighters: the desire to risk it again, to live a ‘full’ life,” he wrote in a diary entry translated by The New York Times. “It’s the so-called ‘gunpowder poisoning syndrome.'"