Quoting my experience,
Stop by security guard for shooting, guard talk in walkie talkie to his chief, chief came down, ask for purpose and particular, told him that permission had been granted by the Property Manager, which in term is his superior, stating the name of the PM, chief called his superior and things trash out. Shooting continue, plus ; if you need any help please let us know.
The above scenario applies to thro' proper procedure, or SOP.
For casual shooting, I'd got found out is b'coz due to the numerous cctv installed, those sitting in the FCP will radio the guard to approach me. Since I had no permission, I'd better take their advice and leave.
As for shooting people/stranger in public place, whether on the street/roadside or in any building/premise it all depend on their culture and charactor.
According to one of my friend who is very good in striking up a rapport with stranger, his advice...
Always ask first before you shoot, that will safe a lot of trouble.