Put this clip right before the confrontation in your edit, then follow it with a pew pew for the fake shots and a shocked sound for the reaction shot to close the scene.
About this sound
This clip is the sharp mechanical rack of a shotgun being pumped, the metal slide pulling back and snapping forward in one quick motion. It feels tense and threatening on its own, but in a meme or prank setting that same threat turns funny and over the top.