The easiest, in my opinion, way to do this is loading up "The Village" level in score attack mode. Or you could just continue your game and progress back to this same point, and there should still be a pack. By the river there's a burnt log cabin with empty bottles inside, craft a Molotov and then walk outside the cabin and throw one at a boar. You will need to directly hit the boar with it. Here is a video to help:
credit to 360gameTV for the video.