Greetings!
Well, I recommend that you send an unrelenting, stern message to the players, that such arrogant lawless behavior will not be tolerated! To wit:
"An attack upon soldiers of the King is the same as an attack upon the King himself!"
Therefore, the whole party should be rounded up, arrested, and tried by the Royal Magistrate. The party should be stretched upon the wrack, and laid into with the Scourge. After this, they should be taken out on a wagon in a procession through the town, with all the jeering crowds taunting them and throwing stuff at them, as they are taken to the stage and scaffold. There, the Lord or Magistrate pronounces the characters' crimes against the King, and declares that they shall be executed by being Hung from the neck until dead. They should then swing high before the screaming crowds!
Then have them make up new characters. The time they put into making up new characters will allow them to think more cautiously and act more responsibly with the new characters, and they most assuredly will be more respectful of the King's soldiers!
I had players that did something very similar in one campaign, and they were arrested, and executed as I described. The whole party has taken a dim view of players acting like ruffians ever since! Believe me, it works!
You, as the Game Master, must set an appropriate example of not only Law and Justice, but consequences for their actions. Forget saving them from the consequences by some form of contrived rescue, or miraculous healing on the part of the victim. They attacked the King's soldiers, and that fact--regardless of the soldier's fate--is a felony. They are thus Wolf'sheads, and should pay the awful price for Treason against their rightful King! No responsible officer of the King should even want to employ them, or trust them with anything. They have shown themselves to be Wolf'sheads, and they should thus die in public execution for all to see, so that all might know the King's wrath against such brigands.
That's my suggestion!
Semper Fidelis,
SHARK