Granted, this was in Baltimore, MD, but it should hold true nation-wide in the USA. It is the law, it is just that most police don't know it and need to be taught. This $250,000 lesson was learned by the Baltimore PD anyway.
Lately here in Toronto a cell phone user captured an office firing nine rounds on a young man blockaded by himself in a street car. The officer fired three rounds and the man dropped, after which the officer fired six more rounds while the victim was on the ground. After that, a supervisor jumped on board the street car and tasered the downed man. CRAZY!!
There were a group of officers surrounding the streetcar and the man was contained.
If it was not for the video recorded, that officer would still be on the streets, rather than now facing criminal charges and time in court.