The Posse Comitatus act still has force. The military CAN'T be brought to bear inside the US borders against US citizens. Even if they did bring in the Military, if ordered to fire on a US citizen, they'd hear the sound of weapons hitting the ground all the way to the UK. I can guarantee that no US serviceman would fire a shot at a civilian US citizen, orders or no. That would indeed bring about an armed revolution, this time with well trained and armed insurgents.
Even at Kent State when the National Guard killed the 4 students, they were only supposed to have blanks and rubber bullets, and the soldiers who fired the shots only did so with that in mind. I don't believe for a minute that it will ever happen again.