Something is stolen or vandalized and you need a report number for insurance. Don't expect your property to be recovered.
You are in genuine fear for your life and you are completely out of other options. No access to weapons or ammo, no path to retreat/escape/evade, etc.
You have resolved a life-threatening issue and you are legally required to notify the police to come make a report, take a statement, draw the chalk outline(s) and haul away the body or bodies.
Other than that, in my experience adding law enforcement to a situation makes it worse.
If your vehicle is stolen or vandalized, you call your attorney, who calls the cops. You do not get involved whatsoever without your attorney, even if you are the victim.