Well, in a MP game, the score is automatically reduced for a TK, or for killing a civilian, and increased for killing an enemy. I seem to be having trouble getting it to display a negative number tho, so I tried:
player addscore 100
in each players init, then when I shot a civilian or did a TK my score went down by 1 point and when I killed an enemy it went up by 1.
I have not had any luck injuring civilians either, they are quite fragile! They go down with 1 shot.
Hope this helps. This way you don't need triggers at all for the civilians if you are not worried about "protecting" them. For protecting them, a scrpt something like this might help:
?(!alive civ1) player addscore -10
?(!alive civ2) player addscore -10
etc....
and create 1 trigger that calls this script just before the mission ends then you don't need individual triggers for each civ