Aslan Usoyan, one of Moscow's most notorious gangsters, was shot dead by a sniper as he left an exclusive restaurant after lunch on Wednesday.

Given the manner of his execution, it's clear Usoyan, also known as "Grandpa Hassan", was a big deal.

Charles Clover, writing about Moscow's mafia wars in 2011 for the Financial Times, observed that the last time someone tried to kill Usoyan it was an intricately planned exercise that led to Usoyan getting shot in the stomach with a Kalashnikov.

This is important because in the Russian underworld the manner you are executed is directly related to your importance, Clover wrote, so a Kalashnikov was a big honor. If Usoyan was shot with a sniper rifle today, that seems to be an even greater honor.

Over the course of the day tributes to Usoyan have flooded Russian social networks, and tabloid Life News has not only published a 3D simulation of the murder, but a graphic photo of the dead godfather's face.

But what does Usoyan's death mean for the Russian criminal underworld? NYU professor Dr Mark Galeotti has written a long post about Aslan Usoyan on his blog, In Moscow's Shadows, which details how Usoyan's death could be an ominous sign of things to come.

"The 75-year-old Usoyan was one of the foremost leaders within the Russian underworld," Galeotti writes, "but at a time when that underworld is going through a process of realignment due to a number of forces, not least the increasing flow of Afghan heroin through the country."

Usoyan, born in Georgia, was an old school Russian gangster — a member of the "vory v zakone" prison gang that dominated illegal activity during Soviet times. He had been to prison a number of times but managed to use Russia's 1990s "Wild East" crime wave to consolidate his position and become one of the most powerful criminal in Russia.

Evidentally he had become very wealthy. The swanky restaurant he was shot outside is just steps from the New Zealand Embassy and the German ambassador's residence. It had reportedly been serving as his "office".

Thankfully, Russia's crime world is nothing like the chaos of the 1990s, but things could be changing for the worse, Galeotti observes, with money from new drugs routes, and the Sochi Winter Olympics has been creating renewed tension.

Galeotti puts forward a few theories as to who killed Usoyan. Russian police seem to believe it was Tariel Oniani, fellow member of the "vory v zakone" who leads a dangerous Georgian-dominated gang from his prison cell.

Usoyan's young nephew Dmitry Chanturia is likely to take over as boss for his gang, Galeotti says. After that, there are only two options: war or peace. And the latter isn't looking very likely.