The scenario you described was the basis for a novel called DON'T TREAD ON ME. In it, a BATF official wanted to boost his agency funding, so he set up a shooting at a stadium, and an unanticipated stampede occurred.
The ensuing loss of life caused a Democratic President to act out his gun grabber fantasies. He learned the hard way that Americans won't give up their guns, adn that given the number of long range rifles (millions of 'em) tht any government that the citizenry opposes CAN kill enough government officials to cause that government to change its behavior.
That is just what the Founders wanted.
Fear not. America is armed, and the Constitution WILL be defended. I am sure that even Nancy Pelosi is aware of this most basic of facts about America.
She knows what that Japanese officer said during interrogation after WW II, regarding why Japan never invaded after Pearl Harbor - "Behind every blade of grass is a rifle".
True then, true now.
That's why the UN crowd wants to ban small arms.
Nutcase Nancy? I am afraid it does not matter what NN knows. IMO NN will spew the commie line and hop in the sack with the "Bring Back the Ban" clan.