Brit is spot on about the vehicles. Doing armed security you encounter people from all walks of life. Many people like to hide in or near vehicles. Other residents in a complex may smoke or chat on a cell phone/use WiFi in a vehicle.
There was a young G/armed officer in the Tampa FL area working a security patrol detail for a large firm called CIS. The security officer was shot in the back of the head in a apt complex parking lot. He died at the scene & never fired a round. This event took place about 3 years ago.