Wow! Thanks for all the facts, figures, and info - most of which has sailed right over my head.
Glad to have helped Cheryl with her 'fix'. No gun ranges close to me, sadly, and speakers on PC not currently working (note to self: nag husband to fix them so I can listen/watch youtube vids
Ok, this is the scenario, changed to take account of your suggestions:
Girl victim sits at desk in outer office. Heroine/narrator in inner office (with window open and construction gang using jack-hammers, outside).
Villain, leaves large bag on stairs, walks up to outer office, shoots victim dead (through heart?), goes down stairs to bag, drops gun in it, then goes upstairs
again and walks in office as if for the first time, and 'finds' victim.