Actually there is a lot of misinformation here. The national guard troops called up so far are supposed to have been all military police troops. Therefore they do actually train with a sidearm. Next some units might not have the M16's loaded but that would be by unit and is a very stupid decision, I might add. The only reason that it is logical to have the NG at airports is to counter a Rome type incident where the terrorists attack the airport because they doubt that they would clear security. If that is the case then M16s are logical. If that is the case, then the fact that body armor and upgraded communications have not been bought on an expedited basis is insane. I have also failed to see much of what I would expect if they were serious about this type of scenario.
Next nearly all of the M16s at the airport would be semi automatic/ 3 round burst capable, not automatic. They would result in many more casualties than what a side arm would do.
Finally to answer the main point of this thread. We have already had this happen since 9-11. A NG soldier from Virginia requested to be called to active duty. He was transfered to New Jersey. While being processed in and before being assigned to an airport, the new unit commander felt that he was acting unusual. He requested a mental eval of him, when other MPs arrived to escort him he attacked them. Final result was several injured MPs and NJ police, I believe 1 or 2 dead but would have to do a search from september/october to find exact figures.
About the same time two AF guards at a Wyoming nuclear launch bunker were arrested trying to sneak into mexico with M16s and a M60 machine gun. This is really no different than some police officers that have been killed after standoffs with other police though. The rate would be less than among the general population.
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Robert