One of Russia's biggest criminal bosses was gunned down in the center of Moscow on Wednesday as he left his favorite hangout surrounded by bodyguards.

Aslan Usoyan, a 75-year-old gangster known as Grandpa Khasan, was hit by a sniper perched on the sixth floor of an apartment building, shot in the head with a round from a silenced assault rifle, the Russian Investigative Committee said. He died at a hospital, leaving behind a nephew he was grooming for succession and the prospect of a bloody turf war. Usoyan controlled prostitution, construction and all manner of protection rackets in Moscow and a wide swath of Russia, according to Mark Galeotti, a New York University professor who has studied the Russian mob for 20 years. The crime boss reportedly had a stranglehold over Sochi, home of the 2014 Winter Olympics, to the envy of the underworld.

Although Usoyan confined his criminal activity to the former Soviet Union, some of his close associates went farther afield. Last year, the U.S. Treasury Department put five of them on a list of transnational criminals belonging to a group considered a threat to the United States. The five were named under an executive order that allows seizure of their assets in the United States and essentially prevents them from banking in dollars anywhere in the world.