Well it goes back to Vietnam really. The idea was that bullets fired by American soldiers towards civilians would automatically turn those civilians into Viet Cong. That was basically the unspoken policy.

Another story was from a helicopter pilot. They would capture what looked like "enemy combatants", load them into a helicopter for transport, then proceed to interrogate them under a threat of being thrown down on the ground. And then they would get the information and throw them off the helicopter But the issue was that they had to count the casualties. So the policy was to _always_ count when disembarking the helicopter not before. As those two numbers were sometimes quite different.