So how do we defined "wild"? Domestic pigs that get loose will turn feral in just a couple of weeks. Their hair will grow longer, they'll grow tusks, and they'll start acting like they were always wild. In my opinion, they're "wild" at that point, regardless of their origins.
That pig may have been born and raised on a farm, but by the time he was shot and turned into bacon and delicious, delicious tenderloins, he was wild.
Wild or not, I would have shot the thing too. I wasn't condemning the man who shot it, just stating what I read.