Veterinary medicine doesn't normally get into forensic type investigations - so most veterinarians would not know what to look for in a situation like this. There may be a simpler explanation - like simple digestive upset. But if you feel it is more I would contact local police, animal control, or humane society organizations that are responsible for investigating cases of animal cruelty. Sadly enough, they may have dealt with situations like this before - or know if there are similiar complaints from your area. It may be that there is no way to tell exactly what happened - unfortunately. I would just be patient with him and his current anxiety. Take him for leash walks only and offer lots of treats while outside.
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