one of our infantry companies was attached to secure a REMF unit during the initial invasion of iraq (this time around, not in '91). those REMF guys acted like fish out of water when they held their weapons. once, all the stray dogs were becoming an extreme menace around the camp and the CSM ordered the infantry 1SG to start shooting the dogs. the 1SG i believe told him something less than satisfactory so the CSM said he would do it himself. he walked outside and approached the first dog he came to and took out his 9mm. he emptied his 9mm at the dog, who was about 20 feet away. not only did every bullet miss, but the dog didn't even seem bothered by the gunfire. he lived to scrounge another day.
We periodically had to do the same thing in our compounds in Vietnam.
Warning was given well beforehand for the troops to get the dogs that were actually pets over to the military vets to be vaccinated and tagged. Only a few actually were taken through the process. On the designated day, the preferred weapon of choice for the cull team was a shotgun with 00 buckshot delivered at very close range. Dogs can be pretty tough animals. Sometimes the first shot was not immediately fatal and a follow-up shot was necessary to finish them off.
Still, even for combat troops, doing the deed was a particularly cold blooded thing to do, since most of the unfortunate dogs were just trying to stay alive and were not aggressive at all; just out of luck.
C'est le guerre.