It wasn't a failure of the gun, but of the holster. It looks like the holster is well used, and after enough use, even the best quality holsters will begin to stretch. It appears that this was the case, and between the stretch of the leather at the mouth of the holster, and perhaps a sloppy or inattentive holstering, it was a set up for an unintentional (there is no such thing as an accidental) discharge.