When in doubt...wait. Probably a couple hours to be sure. If he's already dead, he'll still be dead when you get there. If he isn't, he may bleed out, or at least go into shock, while you're waiting. I had a hit similar to yours this year...looked like good blood, no guts, but I knew i hit him farther back than I intended (he suddenly stepped just as I shot). Clipped the guts, hit liver. I waited a few hours, and found him alive, but unable to move far.

Lesson: when in doubt, wait, and you'll be less likely to jump him if he isn't dead yet.