I remember watching movies where the Nazis were always saying "Show me your papers", how is this different ?

Nuclear weapons should have 'fail safe' devices to prevent a nuclear explosion if the conventional HE explodes. The U.S. has had accidents (aka "Broken Arrows" where 3 of 4 fail safe devices failed and a nuclear detonation was avoided by the narrowest of margins. I recall one broken arrow in North Carolina.

Given the quality of Russian weapons this event scares the shit out of me.