I think you need more than a gun and a girl.
What is the purpose of a ghost? Is it to revisit places that have been significant to the person concerned, or is it to remind others of that person and perhaps to make them inquire further, or is it a stage in the process of letting go from life? Perhaps it is all three.
And how do we 'see' a ghost? Do we have a direct experience, do we perhaps glimpse it on recorded footage or in the corner of…