If it was a double charge, and the odds are pretty great for that, this is a prime example of why you should visually inpect every single case. It's quite easy to see a double charge in a .44 or .45 Colt case if you actually look once they're all done being charged. In 30 years of loading, I've caught exactly two that way.
Too bad about the whole situation. If some jack-boot yahoo anti-gun "person" sees this and puts out there on you-tube, it'll make the whole notion of "ordinary" people beng able to load their own seem dangerous and foolhardy, and give them something else to wine about.