Turns out 'just following orders' is no defense.

"...The “just following orders” defense, made famous in the post-WWII Nuremberg trials, featured heavily in Adolf Eichmann’s court hearings.  But that same year Stanley Milgram, a Yale University psychologist, conducted a series of famous experiments that tested whether “ordinary” folks would inflict harm on another person after following orders from an authoritative figure. Shockingly, the results suggested any human was capable of a heart of darkness... “In particular, acting under orders caused participants to perceive a distance from outcomes that they themselves caused,” said study co-author Patrick Haggard, a cognitive neuroscientist at University College London." ( http://www.pbs.org/newshour/rundown/how-the-nazis-defense-of-just-following-orders-plays-out-in-the-mind/ )

A gun is a near-magical object imbued with the spiritual power and will of its creator: to be designed to kill and a force powerful enough to be credible at it.