Not sure people know or can even imagine what it's like to live outside a city anymore but pet pigs running around loose are not reasonably to be encountered.
Lived in the country all my life, very few country people would mistakenly identify pot bellied pigs as wild boar. Onus is on the shooter to identify his prey and legally follow the rules which he did not, and there is no excuse for trespassing, good intentions or not, in a non life threatening situation . Would you feel as accommodating if he had shot their Newfoundland dog thinking it was a bear? By the way free range pigs are starting to become a very popular niche market for the organic crowd.