A "controlled panic".
Interesting euphemism.
Of course, we only hear the police's part of the story, and who have a vested interest in both bigging up the issue to show they were Doing Their Jobs and in "calming the populace", which is probably where that contradiction in terms euphemism came from. It may well be the two guys were being jackasses, but I'm not prepared to blindly take the police's word at face value, who might've overreacted instead of defused the situation like they're supposed to do first. Not assuming either way, just pointing out it could just as easily be the other way too.