I will not get in to the whole engaging another person with a gun debate as it's friday and i'm going to my niece's wedding.
HOWEVER BE A GOOD WITNESS UNLESS YOU ARE 100% SURE THE OTHER PERSON WITH A GUN IS TRULY A BG
OR THIS CAN HAPPEN. John was 51 not in his 40's as this report soon after the whole incident happened.
http://www.nytimes.com/2012/01/01/ny...bery.html?_r=0
ONE OTHER ITEM
Take a CCW class where they discuss the law and not their career as a LE.
Multiple members here offer quality classes my self included. Starting at the basic level up to very advanced ones in hand gun, rifle & shot gun.