Here's how I implemented a similar mechanic to Counter-Strike 2's Responsive Fog in Godot 4 in 5 minutes.
Resources:
Github - https://github.com/CBerry22/Reactive-Smoke-in-Godot-4/tree/master
Fog Blog - https://godotengine.org/article/fog-volumes-arrive-in-godot-4/
Cs2 Trailer - https://www.youtube.com/watch?v=kDDnvAr6gGI
Fog in Godot: https://www.youtube.com/watch?v=XBJOAK6kNw0
Volumetric Fog in Unity - https://www.youtube.com/watch?v=4QOcCGI6xOU
Models:
https://sketchfab.com/3d-models/training-dummy-3c647d1f74544564bbcafec543743f03
https://sketchfab.com/3d-models/scifi-gun-04a9f3ccb5b14dc38a28b27c1916e18e