He probably died within a few minutes of getting down the hole,,, especially since you saw him running out of steam fast as he headed for the hole. I know how you feel cause that's how I felt in the past whenever I had a a G-hog make it back to his hole after being hit,, but don't be to upset cause the facts that you described all point to a G-hog that died soon after being hit. As for whether it was shot placement or not,,,,, I can tell you that the G-hogs I hit when I did my testing with the Crow Magnums were all hit right in the sweet spot and they still did exactly what your hog did, that's why I decided never to use them again for G-hogs. It wasn't you, it was the pellets. Don't be to upset,,, he expired quickly...
Jeff