On the one hand, yes this was stupid. I mean it really could have backfired badly, and yes the students are traumatized.
However, I remember in High School, I wanted to have a CODE RED drill, so that in the event it DID happen, we might actually be able to protect ourselves. When in a crisis situation, people who normally would function fine, might have panic attacks (I for one am terribly prone to this), and as a future teacher, if I have students who know what to do, then should I start having a panic attack, then there is a better chance of them surviving.
I dunno, my 2 cents.
http://www.youtube.com/huskcharmer