Because it deserved it?
You are right: A Chihuahua?
We have a 10 lb Chihuahua all you would have to do is give her a kick and she would be yelping.
Second: Why would you need to shoot a Chihuahua twice? Somebody needs time at the firing range. Better yet somebody needs a career change.
Because it deserved it?
It was a chihuahua. It had it coming, you can bet on it. They are nasty little creatures.