As a standard action, you can study the weaknesses of a single enemy that you’re observing. Once per day, on a round after you spend 2 consecutive rounds studying the same enemy this way, you can either take a full action to move up to your speed and make a single attack with a melee weapon, or take a full action to attack with a sniper weapon (using the sniper weapon’s sniper range if applicable), against the studied enemy. This lethal strike attack deals damage as normal, and the target must also succeed at a Fortitude saving throw (DC = 10 + half your character level + your key ability modifier) or take 1d6 additional damage per your character level. If the target fails the save, it must also attempt a second Fortitude saving throw with the same DC. If it fails this second save, it dies instantly; this is a death effect.
In addition, whenever you kill a creature using your lethal strike, you can attempt a Stealth check opposed by Perception checks to notice by those in the vicinity; if successful, you prevent those nearby from identifying you as the attacker. If you succeed by 5 or more, bystanders might not even immediately notice that the target is dead (at the GM’s discretion).