I had just turned onto the road that led to our compound.  The gate was only a few yards ahead;  I knew they wouldn't open it until they had me stopped and checked me for whatever they were checking for.  The VC were really good at putting things in jeeps when you weren't looking that made big booms later.  I was slowing and getting set for the turn when something landed with a ringing thud in the back of the jeep.  Processing sounds in your brain can be lightning fast...or sometimes not.  The thud had a vaguely metallic quality and sounded weighty...smaller than a breadbox, bigger than a spitwad.  I analyzed the list of potential thudders and when I came to the "G"s, I skipped right to "Grenade" and settled there.  If it wasn't a grenade, I would be happy to look apologetically foolish afterwards...if it was...well, I had already wasted several micro-seconds in analysis. It was time to act.
I had already slowed to make the turn into the gate so bailing out wasn't as dramatic as it would have been at a higher speed.  Training, which includes the psycho-cybernetic exercise of practicing in your mind things that could happen, took over.  I fell out of the driver's seat onto the pavement, drawing my pistol as I fell.  I hit the ground and rolled up into a kneeling, shooting position, aiming at the area where I felt it was most likely the projectile had come from.  Again the analytical mind went through a series of steps, "...round in chamber, safeties off, front blade focus, steady grip, slow the breathing, re-focus past the sight to the......Commander's driver"?    Hicks, the CO's driver, was frozen in my sight-picture.  He had a quarter of a watermelon in his juice-dripping hand, a look of pure shock and terror on his face, and a noticable rattle in his knees.  He, in chorus with a number of his friends, was yelling for me to not shoot him.  Somewhere in this sequence my jeep, which had continued on without my assistance, had idled into the guards' bunker at the front gate, causing the guards to jump out and take up defensive positions (even though the Islamic terrorists are getting credit for it now, car bombs were a preferred method of the Viet Cong long before anyone ever heard of the Ayatollah Khom...Kohm...that guy in Iran).  I didn't shoot, the guards didn't shoot, and Hicks promised to never throw his watermelon rinds into my jeep again (he had started out with a half a melon).  
Told you all that so I could tell you this.  Less than two weeks later, just after turning onto a side street near the MAC-V Headquarters off Cong-Li Street in downtown Saigon, I heard a thump that sounded a lot like something landing in the back of my jeep.  I gripped the wheel with both hands so hard that it hurt. I leaned forward and clamped my jaw so tight I thought my teeth would break.  I waited like that for the blast.  No John Wayne crap, no rolling, drawing, angry response...I just sat there waiting to be shredded.  Could this be the same GI who had had the lightning reflexes a couple of weeks earlier?  What makes the difference?  I will tell you the truth...I don't know.  Oh.  And by the way, I don't know what made the thump the second time.  After waiting the requisite 3-5 seconds for the boom, I searched the jeep high and low...nothing.  I have spent a lot of thought on those two incidents in my own life.  After more than forty years of consideration I am no closer to explaining it than I was in Saigon.  I have discussed this with other vets, some who had much more dangerous daily duties than I did;  some who didn't.  Most, the honest ones, have had similar experiences.  I am not sure which reaction was the real me.  We all like to think of ourselves in heroic terms.  I am sure no one daydreams of being the 98 lb weakling that gets the sand kicked in his face.  We all see ourselves as winners: saying the clever things, standing up to the bullies, winning the hearts of the fair ladies.  And in cyber-space we can be whoever or whatever we want. But no matter what image we conjure up for ourselves, the mirror is always right there and it doesn't always support our version of things.
Maybe the factor that weighs the heaviest in these examples is the fact that I was alone.  There was no one else in the jeep, no one who needed my support, no one who counted on me to do something or make a decision.  No witnesses.  Just me and what the Brits used to refer to as "the Elephant".  Well, I saw the Elephant on many occasions, but most of the time in a group.  Being alone may be the one thing that makes these episodes different.  So then, why?  Why two diametrically opposed reactions?  Here's what I think:
We just don't know.  Those of us who train for violence, who practice dealing it, and who live with its imminent threat, think we know.  But we don't.  Each episode is its own autonomous play.  The actions we undertake, or don't, are dependent on so many variables that they couldn't all be listed here.  But mindset, expectations, environment, what you had for breakfast...they all play a part in determining what happens next.  That is why we train so hard in the military.  We train on things repetitively so that when the rubber meets the road, when the brain starts getting analytical, when the sphincters start to loosen, the mouth gets dry and the hands get wet, the training kicks in and you do things that don't require active analysis.  Sometimes it takes the brain a full second or five to catch up to what the body has already undertaken...a time frame that you could barely fit the blink of your eye in but enough to make the difference between life and not.
What started this train in my brain was the thread that Tova had on her page last week about the school board shooting in Florida.  She was kind of tough on the guys who sat and watched the purse lady risk her life on their behalf.  And maybe they deserved it. 
At the assassination of Anwar Sadat, the shooter jumped off a vehicle passing the reviewing stand, ran up to the stand and started shooting his AK-47 at the Egyptian President at point-blank range.  Some other folks got shot, too, but not on purpose;  they were just there.  The people around Sadat reacted in an interesting way.  One of the men grabbed a folding chair and threw it on top of Sadat.  I guess his reasoning was that it might slow down the bullets or something.  But within seconds, a whole bunch of folks were throwing chairs on the President;  maybe ten or twelve of them.  It didn't save his life;  I don't know if it even slowed down a bullet or two, but the non-targets saw someone take an action and they all jumped in.  Probably not the best idea but possibly the only one anyone had.  And they were acting, which feels better than not.
So the school board guys, who sat indecisively watching as the gunman worked himself up to the pull-the-trigger level, didn't have an idea.  They may not have had any training to fall back on.  They watched and then ducked when the bullets started flying.  Maybe if they all had had a purse they could have joined in.