How far away?
There's no doubt that a big whitetail buck is tough. I shot a nice 10pt this year at just over 220yds. The Barnes bullet liquified his vitals and he still went 50yds. I think that's just how much adrenaline they have in their body. I've ran 1oz slugs through em at 20 yds, blowing fist sized holes all the way through em, and still had em take off. Tough critters. But, that is a nice deer you got there. Congratulations on the hunt. What state is that?