Depends.
If the perps are Left Wing or Moslem terrorists, it will become a law enforcement operation and allowed to die.
In the unlikely event the perps are right-wing, it will become a major crisis, requiring massive para-military operations against thousands or tens of thousands “right wing domestic terrorists and their sympathizers.”
Either way the result will be an increase in government power (DHS , big sis etc) with a corresponding decrease in individual freedom and rights of law abiding Americans( a cracking down on Americans and taking away of their gun rights). nothing will be done to foreign Muslims who caused it
But this is the result of every crisis real or manufactured