I know it sounds sick, but what might've happened is that the little guy ate some poisoned meat. There are some random jerks out there who throw pieces of meat that they doused in antifreeze or rat poison into yards with pets, who eat them, get sick, and die within hours. It's almost too ridiculous to suggest, but it happened to my aunt's dog and a few years later to my friend's dog.

My first post, by the way. I'm new to toking and these boards alike.