Place it at the end of an investigation scene, after a notification cue and just before the scare lands. Open with the Fears to Fathom notification sound to signal activity, follow with this reply as the reveal, then cut straight to the FNAF jumpscare scream for the payoff.
About this sound
This is a sub-second Phasmophobia spirit box reply, a distorted ghost voice answering through the game's radio-like device with a short, clipped phrase. It feels eerie and unsettling, like something unseen has just spoken back in a dark room. The clip comes from Phasmophobia, where players use the spirit box to ask ghosts questions during an investigation.