In all likelihood there have been NO cases of an accidental wounds of deaths in firearms history that were not related to violations of 1 or more of the 4 basic safely rules for handling firearms.
(Even back in the days of flintlocks and earlier, ALL accidents were a violation of the basics of gun handling despite the fact that the rules themselves had not yet been written)
#1 Treat every firearm as if it’s loaded at ALL times.
#2 Keep your finger off the trigger until your sights are on target.
#3 Never let your muzzle point at anything you are unwilling to put a bullet through.
#4 Know your target and what is around and behind your target.
As a gunsmith I think I can say I understand the working of firearms better than most people. I earn most of my living working on restorations of antiques and recreating flintlock arms. Also, I have been doing general gunsmithing now for 44 years.
I can absolutely assure you that "documentation" of firearms "going off" in both the press and also in police and military reports are usually BS. The "documentation" is nearly always written to (A) Avert blame for negligence or (B) foster a political anti-gun sentiment in the eyes of the reader.
Just because it's "documented" doesn't mean something is true. It means it was written on a document. Nothing more.
A gun cannot "go off by itself" any more than a car can drive itself. Or a chainsaw start itself and wield itself.
A SA auto like a 1911 could possible break a sear nose or the full cock notch could be worn to a point that it would not hold, but the safety will still prevent the hammer from moving until the safety is unlocked and when that was done the hammer will fall into the half cock notch (what it's actually for on a 1911. It's NOT a safety notch!)
The only firearm I know of in which a breaking sear could cause the gun to go off is a flintlock with a fly in the tumbler. The fly is a cam designed to prevent the hammer from going into half cock when set triggers are used. If the nose of the sear was to break due to metal failure that hammer would drop to hit the frizzen. In MOST cases I’d have to say the gun still would not fire because the flint would move only about 1/8” to ¼” before it hit the frizzen and probably would be unable to make a spark, but I would not say it’s impossible. I will say it’s still impossible to have a bad accident if the 4 rules were being obeyed however. The muzzle should be pointed in a safe direction