While I hate to bring up nationality as an issue here, I have found the South of the Border natives generally have a really low regard for cats compared with dogs.
And the fact the nail was driven into the head with a nail gun, also points to the high probability it wandered onto a construction site with mostly immigrant workers.
I have also heard of people feeding young kittens to reptiles before, and keeping multiple female cats, and even small dog breeds, around only as breeder animals for this purpose. In fact, I suspect some neighbors across the street who have reptiles of doing this very thing. They also have about 8 small Chihuahuas, many in various states of pregnancy, too. They also just "happen" to be breeding dwarf rabbits, also most likely to feed their hungry reptiles to. But how would one prove such a thing, without catching them in the act?
This is why nobody should just "give" away free kittens and puppies on a site like Craig's List. Even if you only charge $10 or $20 bucks each, you will discourage these heartless scumbags from feeding them to their reptiles for free. And a red flag would also be someone showing up and taking ALL your litter away at one time, for some BS reason they might give you.
Just get your pets FIXED, and you won't have to worry about an unwanted litter of cute babies being used as reptile food, or to train fighting dogs with.