Demetrius ~
That's a horrible story. What an awful thing for the man to live with for the rest of his life!
http://www.corneredcat.com/Safety/fourrules.aspx answers the question you asked in your first post, as does
http://www.corneredcat.com/GunCare/cleaning4rules.aspx
In order to avoid doing something like this, you simply have to be seriously, obsessively, and persistently dedicated to following the safety rules
no matter what. For a tragedy to happen, at least two of the Four Rules have to be broken at the same time. If you habitually follow
all the rules, then when you make a human and understandable error in breaking one rule, the other three rules will still be there to save your butt and maybe save a friend's life too.
Thanks for posting the update.
pax