I first thought these circles were from the shock of the bullet impact or then again it could be like the story of the Calvary officer riding through a small Southern town during the civil war when he comes across a barn with several bulls-eyes with a bullet hole dead center in the middle of each one. See’n an old farmer walking by he asks: do you know who shot the holes in this here barn. Oh sure, the farmer said, that would be Billy Joe – lives down the road a piece. The officer says; well, anyone that can shoot like that should be in the Calvary. Well, I recon you should know that Billy Joe is not right in the head, the farmer explained, ya see, he’ll come out here and shoot holes all over the barn – then he’ll draw circles around each one.

That could be what happened here.