How do I give a death sound to an npc?

If the NPC gets

:Destroy()

then simply all you got to do is insert the sound to the NPC model and set the sound to "Play on remove".

Whenever the NPC model gets removed, the sound will play.

If this helps, please accept this answer as solved! Thank you!

Edit: If the NPC doesn't get "removed" then please let me know!