I don't know when, exactly, it started.
I do know that by the mid-'80s, any reasonably well-informed Soldier of Fiction reader knew that the British SAS did an annual exercise involving real live bullets flying about as they "rescued" real live members of the royal family sitting amongst cardboard bad guys. This became the de rigueur thing to do for any unit that prided itself on its innate awesomeness and elite-itude. Not having a royal family handy, the FBI's Hostage Rescue Team would happily "rescue" any old visiting VIP's in a live ammo shoot-ex, one-upping the Brits by using NVGs and doing it in the dark.
By the turn of the millennium, civilian attendees at some weekend gun camps were standing next to targets that were being shot at by their fellow weekend gun campers, supposedly to "inure them to incoming fire" or something. At some level, a healthy respect for the business end of a firearm and what it can do to human flesh had been lost.
The world got an awful reminder on the last weekend in June, when a team of elite French para marines turned a public demonstration of a hostage rescue into a "How Many Of The Four Rules Can You Break At Once?" competition, Team Category.
For whatever reason, perhaps dramatic effect, the troop laying down full auto mag dumps from his FAMAS rifle as suppressive fire was doing it right at the crowd. When his first mag, which was full of blanks, ran dry, he dumped it in a fast mag change and slapped a second magazine into the weapon, ripping it off downrange as well.
Only the second magazine wasn't full of blanks.
I've never gotten a close look at the Blank Firing Adaptor on a FAMAS, but apparently it was sturdy enough to cause much of what went downrange to fragment. Even so, 17 people wound up hospitalized for one moment of idiocy.
The Four Rules are devised so that at least two must be broken to put holes in something you don't want to. In this case it was Rule One ("All guns are always loaded,") and Rule Two ("Never let the muzzle cover anything you are not willing to destroy.")
The Four Rules are the Four Rules. No matter how tactical you are.