"Use 2 Sleep Darts on Gunners" is an optional mission objective in Sequence 5 / Memory 02: Unmanned
Walkthrough[edit]
As you make it through the sugar cane fields toward Prin's estate, you will find numerous towers with Gunners on them. Approach them from a Stalking Zone then hit the Gunner atop them with a Sleep Dart. Just tag 2 different Gunners with Sleep Darts to complete this objective. This can be done on the approach, going for the Gunners in the Watch Towers or when you make it to the house tagging the 2 Gunners on the roof of the mansion.
