To make it more realistic...
Have them be men in civilian clothes. If they pick up a weapon, they're insurgents. If they don't, they're civilians. If they shoot you, drop the weapon and run, they're civilians again. All the dead ones are civilians, because they don't pick up weapons and their buddies strip any weapons off them. Then throw in little kids running ammo, thirteen-year-olds shooting at you, and insurgents basing themselves in people's homes with the cowering residents.
It ain't easy being a Marine.