No game is fun when there is no penalty for losing. In this game you'll have to pay the ultimate price if you fail.
The situation seems highly unfair, as you're staring down the barrel of a gun and the other guy only has the risk of spraining his index finger.

Luckily the adrenaline rush has raised your senses and time seems to slow down as the trigger is slowly pulled back. It only takes a few milliseconds to determine if you are a total hero or a complete idiot.

Dodge the bullet in time.
The time you have to react is indicated before the showdown.

Left click as fast as you can when the gun is fired.
You’ll receive a penalty when you click before the gun is fired.