It seems to me that we do not have enough details, and if the distance really was 200 yards (meters), then that is a really expert-level kind of shooting, especially with ONLY one shot.
I don't know why people keep repeating this retarded shit.
200 yards is nothing, a child could make that shot as long as they can line up the long rifle.
I could literally make that shot at 500 meters in the offhand with a carbine let alone the prone with a long rifle.
They said it was a Mauser 30-06
Which is too long to fit in a knapsack.
They have a photo of him jumping off a roof with no rifle.
Yet the rifle was found in the woods.
So someone else helped with the rifle or he modded the rifle and made it be able to detach the barrel.
It is not meant to detach it is compression attached when the threads are mated.
Wonder what the story is.