Even if it is an antique muzzle loader.
Apparently, the other 3 rules were ignored as well, and a 3 year old boy is dead because his father was careless and stupid.
A few weeks back, I saw a big stink running around some of the gun-blogosphere about the 4 Rules, especially Rule 1. I stayed out of it, because I got tired of arguing how many angels could dance on the head of a pin long ago. I guess now I'm going to say my piece.
The 4 Rules (or the NRA's 3 Rules or whatever set of safety rules you want to embrace) are there to keep these things from happening. Col. Cooper's Rule 1 is the most basic safety rule: "The gun is always loaded." That means treat the gun like it's loaded--even if you and 3 other people have all confirmed that it is fact unloaded and it hasn't left your possession for a microsecond since then. You still treat it like it's loaded--no pointing the business end at something you don't want to kill or destroy, finger off the trigger and so on.
And for the record, no, I don't approve of simunitions and I think all force of force training should be done with blue/red guns or Airsofts. Live-fire houses? Only if I'm the only one armed and the instructor is behind heavy cover. Why do I go against the opinion of the multitude? Because mistakes happen--and I don't want to be one or commit one.
If you still want to argue the point, go to Union County, North Carolina. I suspect there is a Dad there who wishes he had followed Rule 1.