If I had any bets to make , I would say it was a contract hit gone bad, done by the Russian Mafia.
If it was KGB, our good man would be deader than an old blind country road killed skunk.
I deleted part of my previous post - got too wordy - but I would not be surprised if the KGB and Russian Mafia are not intertwined. By that I don't think we can discount the tentacles of the Mafia within the KGB. I even wonder if Putin is nothing much more than a figurehead these days. Although the attempted assassination is intended to frighten into silence certain people - has the KGB ever been so brazen to publicly assassinate an American on US soil before?
Just an uneducated opinion.