The scary thing is lots of people with lots of authority will do whatever he asks them to do. If the military won’t do it, he’ll find someone who will.
That someone who will do as he orders, will end up being kicked down by the others who won’t be willing to let it happen. As it is, the entire country is on the verge of full blown rebellion against the President, on the borderline of marching on the White House itself and there is no way that any sane military will be willing to pull the trigger on the citizens they swore an oath to protect. There might be others, but during a full march, a few dead Americans means a painful death for the people who pull the trigger and the ones who order the shooting of US citizens.