Silent Kill

Combat

You are quite adept at killing your prey without making noise or alerting others.

Prerequisite: Stealth 12 ranks; assassinate† advanced slayer† talent or ninja master trick.

Benefit: When you kill a creature during a surprise round, you can attempt a Stealth check, opposed by the Perception checks of potential observers, to prevent them from noticing your action and subsequently identifying you as the assailant.

Source: Advanced Class Guide