Many countries have protocols in place which determine who the successor to the leadership of that country will be in the event that one or more of the leaders or their successors die.
What is Russia's chain of succession? My research indicates that if the President is removed, the prime minister succeeds him, but what if the prime minister is also removed? How is the chain of succession determined?
At what point of simultaneous removal of political office holders or those appointed by them does the chain of succession become unclear even to the Russians? Who is likely to be in charge at that point?
To make this more clear, I'm talking about a potential assassination and/or terrorist action that more-or-less simultaneously removes the President and a variable number of his successors. I'm interested in knowing who could take immediate, emergency, leadership of the nation and have the power to act to resolve the state of emergency. Don't tell me that there wouldn't be a state of emergency if the President and a lot of his successors were killed.
Restoring the day-to-day government is beyond the scope of this question.