Thanks for the answers but I managed to eventually solve it.
To disable the movement without keeping the momentum, since this was being called from another script, I just had to do this:
$Player.movement = Vector3.ZERO
GlobalScript.movement = false
At first I tried setting velocity to Vector3.ZERO but it didn't work out. However, setting vector3.Zero to movement completely stops the player, and then it completely disables the movement by setting the GlobalScript variable to false