From: Officer.com
The basic premise for The Red Zone, a one day class I recently attended in Camden, Tennessee was that during an actual life or death encounter there are far more things that should not be shot than those than should be.  Johnny Jihad is evil and can shoot up the landscape. You are the good guy and cannot do so. David Biggers former U.S. Army Officer and dedicated student of the gun led a dozen men and women through several drills designed to force the shooter to fire their defensive pistols in a deliberate and discriminating manner.
Up Close and Personal
The FBI compiles the most thorough statistics of actual gunfights in the United States. According to the 2009 stats, 19 of the 48 officers murdered in the line of duty where a firearm was used were 0-5 feet from their attacker. We’ve all accepted the 21 foot average, but the truth seems to be that 21 feet is more likely to be the outer limit than the minimum.