The answer can be found by posing the following hypothetical question:

You're walking down a deserted street with your wife and two small children. Suddenly,an Islamic terrorist with a huge knife comes around the corner, locks eyes with you,screams obscenities, praises Allah, raises the knife, and charges at you. You are carrying a Glock cal. 40, and you are an expert shot. You have mere seconds before he reaches you and your family. What do you do?