Several years ago I was at a gunshow where this happened rite behind me. I had just checked out a early GCNM at a table very well even checked the bore and mag and was going to look around a bit more before making a offer. I am absolutely sure the gun or mag was not loaded but I was two tables away when it went off. After I climbed from under the table I found it was the same gun I was looking at.
I have no idea who loaded this Colt but I know it was not loaded when I checked it.