Two of the three suspected Chechen militants gunned down in what appeared to be a professional assassination in Istanbul last week shared a link to one of the deadliest terror attacks in Russian history.
Rustam Altemirov, who Turkish police said was shot by an assailant with a silenced pistol on the street in broad daylight Friday along with two other men, was charged in absentia in June for his alleged role in the suicide bombing of Moscow's Domodedovo airport in February, according to Russia's state news organization. The bombing killed 37 people and injured over 100 more.
Another of the men killed in Istanbul, Berg-Khazh Musavei, was a reportedly "close associate" of Chechen terrorist Doku Umarov, the man who bragged in a video online that he was the one who ordered the Domodedovo bombing as well as an earlier deadly attack on Moscow's subway system.
READ: Chechen Militant Claims Credit for Moscow Airport Bombing
The third victim in the shooting, Zaurbek Amriyev, has also reportedly been linked to Chechen anti-Russian operations. All were killed the afternoon of Sept. 16 when the assailant fired 11 shots in less than 30 seconds from a silenced pistol, including several headshots, according to major Turkish news reports.
The Turkish reports said police received a tip Monday as to where the assailant was staying, but arrived just minutes after the killer slipped away.
But the supposed assassin left in such a hurry that his equipment -- including the silenced pistol, a night-vision camera and binoculars -- were left behind, as well as a passport identifying the suspect as a Russian citizen named Zharkov Alexander, the reports said. Ballistic tests on the gun reportedly showed it was the one that had been used in the triple murder.
A Turkish official told ABC News Wednesday the country's intelligence service was investigating whether Alexander had any connection with the Russian government -- an accusation already leveled by Chechen rights groups and media, who said he was a spy for Russia's intelligence agency, FSB.
A spokesman for the Russian Embassy in the U.S. said that any implication the Russian government was somehow involved in the killing is "pure speculation having nothing [to do] with reality."
Brad Garrett, a former FBI agent and now ABC News consultant, said that whoever the killer is, he appeared to be a professional.
"This clearly looks like an organized kill... it doesn't have any flavor of a street crime," Garrett said. "The silencer, that even adds to the belief that this was an execution... I would say he's somebody that was sent to do what he did."
As Turkish police continue to investigate the killing and chase down Zharkov, one Russian official involved in the North Caucuses offered a blunt opinion on the assassination to Russia's Izvestia newspaper.
"If those killed were really involved in suicide bombings, then everything that happened is a normal phenomenon in the war," Maxim Shevchenko, head of the working group for the North Caucasus of the Public Chamber, told the paper. "They've declared war on the Russian state, and it is logical that the security services respond with a group of liquidators and cleansers."
ABC News' Dragana Jovanovic contributed to this report.