Secret Assassins is a new gamemode in which all players are disguised as strangers and are plotted down into the map with 50+ actual strangers. The aim of the game is to observe peoples' behaviors and identify the players to kill them.

There are 3 kits that you can choose from: The Escape Artist, Ranged Assassin, and the Revealer.

That's the basic guide and explanation of the Secret Assassin Game Mode, here are some tips:
Walk around and stop to look around every 2 seconds.
When you hit an NPC, try to turn around and walk into a large group to avoid detection.
When someone hits you, throw a smoke bomb and run away as fast as you can!

Be aware of monsters and zombies