Thoreau and Mencken were both right!

While poking around on the Web yesterday I ran across a pretty cool site:  brainyquote.com.  While skimming through there I ran across two quotes from two different people.  I've heard each quote, but never thought of them in tandem.

Henry David Thoreau said:  Most men lead lives of quiet desperation and go to the grave with the song still in them.

Most everyone has heard of that one, but then I ran across this one that I think is far more interesting, and far less well known.

H.L. Mencken said:  Every normal man must be tempted, at times, to spit on his hands, hoist the black flag and begin slitting throats.

These two thoughts are true because fairly often one sees the interview on the news, or reads it in the paper, where the neighbor of the guy who just ran amok with a machete at the farmer's market, professes disbelief.  "I've know the guy for thirty years.  I can't believe he'd do something like this!  He (insert your favorite redeeming characteristic here)..."

My question is if, most men lead lives of quiet desperation  and if every normal man must be tempted, etc, etc, etc...what percentage of the guys next door are time bombs waiting to go off?

More importantly, what is that trigger that will set these guys off?    We can guess at what we think might be normal triggers, 14 year old junior wrecks the family Ford while drunk on underage booze, the wife runs off with his best friend, or that his local chapter of the Jackbooted Corporate HR Thugs request a meeting Friday afternoon at 3:00; or maybe his 12 year old little girl comes home and proudly announces that her due date coincides with her junior high graduation date. 

The interesting (and scary) thing for me, though, is that as human beings we all tend to get worked up over all sorts of odd, and usually inconsequential, happenings throughout the day.  Someone takes the last of the coffee at the office and doesn't make a new pot, or the Mega-Mart has a sale on just the widget that we're looking for, but is sold out when we get there, etc, etc, etc.

So I guess if both Thoreau and Mencken were right, then the people we should be on the lookout for are not the obvious murderers, but the ones who just seem to be normal, everyday people just going about their business.