The simple fact is that to take a pre-emptive strike might cause you to be alive while otherwise you might be dead. As silently as possible, you draw your sword. Then with extreme slowness, you begin creeping up on him. He seems lost in thought and doesn't seem to notice you. Then when you're about ten feet away from him, you hear the sound of grass crunching beneath your feet. You see the expression of surprise on his face as he sees you with sword raised.
With lightning speed, he pulls an arrow from his quiver, raises his bow, cocks the arrow, pulls back the bow string, aims, and fires. Then in an instant, a blinding flash, you see a blur, then thunk, the arrow goes through your chest, piercing your heart, you fall backwards, hit the ground, you open your mouth as if to scream but make only a faint wheezing sound. Your sight, hearing, and sense of touch leave you in that order, leaving only an unfathomable pain that courses through every fiber of your body, as your blood sloshes and stains the grass. As the pain causes you to finally pass out, the first and last words to form in your pain-blinded mind are "...Oh Anu!..."