It has been my experience that a deer needs two alarms from the hunter to run.
If he sees you move your hand, he is on alert, and will look at you.
If he is on alert, and hears your trigger click, he will run.
If he smells you, he will go on alert, and look at you.
If he is on "smell alert", and sees you move your hand, or hears your trigger click, he will run.
If he is not on alert, and hears your trigger click, he will look at you.
The next thing he will see will be the cloud of blue smoke from your muzzle.