Man of Honour
Thinking about it, it might make more sense that if you roll and pass the accuracy score, you hit the Walker, but if you fail, you hit the survivor. That would make spraying a zone with something like a shotgun or assault rifle really dangerous with a survivor present as you're likely to hit them at least once, but with something like a pistol it could be worth the risk.
I'm just quoting myself because this is the house rule I brought into our games months ago, which I know a few people here disagreed with. Turns out the developers agree with me, as this is now the official rule for the Black Plague edition. About time too