The story and mutilations look very similar to the epidemic of chupacabras attacks that we had in Argentina in 2002. It was covered for a month by all the major newspaper and TV stations. [spoiler alert: it was just the misclassifications of the result of mice and foxes and other animals eating the corpse]
Autotranslations:
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EDIT: Perhaps you can put a bluetooth detectors in the necks of the horses that sends a signal to your home. I guess the attackers will forget to turn off their cell phones and you can try to detect them. (Anyway, my main hypothesis is that is a misclassification.)