Before we all go on about what the Geneva Convention requires, we ought to, maybe, read it. One of the requirements for a combatant to be protected by the Geneva Convention is that he carry his arms openly.
The enemy combatants in Fallujah had, based on other statements, frequently used wounded and dead as decoys to hide weapons-- i. e. booby trap.Thus they are not entitled to the convention that requires the U. S. to protect the wounded. They violated other conventions by failing to dress in distinctive garb that would allow the Marines to tell from a distance who is a civilian and who is a foe.
If we are going to talk about the geneva convenations, maybe we should read them.
Reference Guide to the Geneva Conventions