Imagine shooting live bullets when fake ones were supposed to be used

This is the worst nightmare of most people in the defence services, especially during shows meant to showcase the abilities of the military. It is often necessary to stage events that are very realistic, such as the simulated saving of hostages from terrorists, fights with terrorists in urban landscapes, etc. In many such situations, the public can be very close by, having been already informed that the bullets being used are fake. Now imagine the panic and horror when these bullets are fired, but they are not fake, and are instead real ones. Such an incident happened recently in France, and resulted in punishments for many of the soldiers involved, including the moral-grounds resignation of the head of the French Army, General Bruno Cuche:

Paris: The head of France's army has resigned following a weekend shooting at a military show that injured 17 when real bullets were used instead of blanks, the French presidency said on Tuesday.
The defence minister, meanwhile, suspended the use of blank munitions at military shows for the public. Investigators are looking into Sunday's display of hostage-freeing techniques at the Laperrine military barracks in southern France. Most of those injured were civilians, and three were children.

This was apparently a mistake when the ammunition was being loaded; it however seems a clear case of negligence at the minimum since the concept of having live ammunition nearby when fake ammunition was supposed to be loaded (along with no cross-checking) seems a bit strange.