I think that you can set the Civilian enemy to OPFOR in the screen where you can change weather, fog etc. Do that and make an array which includes all the names of the civilians (if there aren't too many of them).
Use this line in a script, trigger etc.:
{ _x setCaptive true; } forEach [c1,c2,c3,c4,c5];
to make them enemy to OPFOR again, use:
{ _x setCaptive false; } forEach [c1,c2,c3,c4,c5];
(there is no east friendly to thing)
You could try to give the civilians a negative rating: c1 addRating -10000
That should make the guards fire at them.