Weapons accuracy is not their bosses first priority. It ranks 24th on a list of 24 items they are evaluated on.
"One checklist that is used to evaluate marshal performance leads with "compliance with dress code" and "compliance with grooming standards." The last item, No. 24, is "weapon handling skills and safety."
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http://www.forbes.com/entrepreneurs/feeds/ap/2005/12/09/ap2381208.html
So, just to keep the discussion going.
Lets see if I can recap this. Passengers are reboarding after having their bags inspected by customs. Agitated Man rushing up center of plane. Worried wife following him, yelling that he was suffering from Bipolar Disorder and needed to get out of plane. Man enters jetway with enthusiastic fed following. They order him to stop and he reaches for his bag. They shoot him, then realize that they need a more valid reason than "failure to comply with a lawful order by a law inforcement officer". They think they heard him say something about a bomb. No one else hears him say that. Is that about what has been reported?
To me the following would indicate that caution should be used before using deadly force.
1. The bag had just been inspected, so probably did not have unauthorized items.
2. The wife informed them about why hubby was acting that way.