I don't know what to think. My initial thought is that it had to hit something of substance because it didn't completely pass through. If it was just a flesh wound, I would have thought it would have blown through that deer. Maybe those backstraps just constricted and grabbed that arrow. But like you said, the way he ran off, he didn't seem all that phased. What weight are you pulling, what broadhead, and what is your arrow weight. Just curious?