I agree with MLeake that there are some people out there that seem to enjoy killing for the sake of killing even more than feral cats do. It's too bad as a fairly small number of people give hunters and gun owners in general a bad reputation.
That being said, I completely understand eliminating animals when they become pests, or are putting your pets/livestock/property at risk. I've had to shoot countless squirrels to keep them out of the house, and I've even shot a few feral cats that came around looking for a fight.
So I can see both sides.
The biggest thing I got from this story though, is that next time I do have to kill something I should seize the opportunity to turn the experience into a good story.