It is not a "spontaneous discharge" but an accidental discharge due to impact. 1911s have the ability to discharge when dropped unless modified with something like a firing pin safety. Series 80 Colts have this, but the Colt in the incident did not.
Ah, but this one did have a firing pin block, as explained in the article and shown in Fig. 2d.
Jim's Rules of Carry: 1. Any gun is better than no gun. 2. A gun that is reliable is better than a gun that is not. 3. A hole in the right place is better than a hole in the wrong place. 4. A bigger hole is a better hole.
no guns = might makes right