Firing upon your own military is treason. They should be charged accordingly and executed accordingly.
"Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court."
Firing on your uniformed soldiers during a time of war is certainly "levying war against them", IMHO.