The assassin

WTF. Why is he just staring at you. You take a step towards him but he keeps on just staring.
WTF you think again. You touch the guard and he falls down unconscious. You look down at him and see a needle in his neck. You pick it up and smell it.
"Knockout serum," you think to yourself.
You drop the needle and look around. You see nothing so you listen very carefully. Yes. You found him, you think. If you have this right, he is above you...NOW!