I see no reason to suggest it is anything to do with Arabs or Moslems.
It appears to be a contract killing, either by Russian gangsters (there are plenty of them) or by an authorised or renegade Russian secret service (and there are plenty of them too). the man was (1) a traitor who has left a Russian secret service and defected to the west (2) an irritant who has been criticising Russian gangsterism and crime, both private enterprise and state-run, so he made plenty of enemies..
It does seem to have been an strangely complicated way to kill someone. Most of the contract killings are 2+1 shootings.