Where I hunt the woods are thick they run out of sight in a hurry.What I've learned to do is listen.When you can't hear him running anymore and the woods are quiet just keep listening,you may hear him fall over.
Numerous times I've heard deer crash after they were out of sight.It may only take 30 seconds or a few minutes.Once I shot a deer and he took of running.About 5 minutes later I heard a noice about 50 yards behind my stand.I thought it was another deer because the one I shot ran in the opposite direction.It turned out that he had circled around.