I disagree. It looks like they are releasing captured hogs. All the hogs seem to originate from about the same spot. Yes, I have seen sounders run. I have also seen sounders bolt in the a myriad of directions when been shot at by hunters.
Not only that, but with all the folks standing around, it does not look like these guys are at a choke point in the middle of the field. You can tell by the shadows and voices that there are quite a few people standing around to watch and that the camera is careful to not show where the pigs come from. Not only that, but the pigs materialize just as the shooter gets ready.
It is legal, but I am not sure that it is really eradication in the intended sense of the word if you capture them and then release them again.
I am curious about the structures in the distance. I failed to notice anything of a proper backstop.
"If you look through your scope and see your shoe, aim higher."
-- said to me by my 11 year old daughter before going out for hogs 8/13/2011