Yes, I did say, "MOST" for a reason.
Understand, that you are standing in a dirty alley, with a dude with a knife threatening you. This does not apply to a stab in the back without warning (Which was most likely a deep penetrating wound that severed a blood supply or an organ, in which case fatality is a high probability). In most cases the BG does not have a Kershaw, or Benchtop, or Spyderco, or even a Case. He's got some POS cheap made-in-pakistan steak knife he stole from a Denny's or shoplifted from Wal*Mart. Don't get me wrong: You can get just as dead from a cheap POS knife as you can from a KA-BAR. The times I have had knife-showing BG's toe to toe with me one was a POS steak knife the other was a Flea Market bowie knife. Both ended without a shot fired and no money was lost. I hav ealso been threatened with bottles, a chain, random pieces of metal or pipe, and a couple times with tire irons.
(FREE TIP: When you start working graveyard for a wrecker company you get all the great calls. Be in the habit of knowing your surroundings very carefully)
I'm talking in this case about face-to-face with an arm's length between you. You have a free hand for a reason, use it to gain space to draw and fire. Defensive wounds to your arms will bleed a lot but usually heal well. Your 3-6 holes in BG's chest will usually NOT heal well. As I have preached before, surviving these types of encounters comes down to one thing: Seizing and maintaining situational dominance. You must dominate the situation, if you show weakness or hesitation you will most likely trigger the attack from the BG. Most BG's are used to targets who are afraid, cringing, nonviolent, and never fight back. A confidant, dominant, calm and assertive target who does not comply, takes an aggressive/defensive stance and draws a weapon with skill and knowledge in every motion WILL surprise them in most cases, thus ending the assault. Don't pull the hollywood badass crap, spouting some line you heard from some shoot-em-up movie. Present your weapon and your determination to use it simultaneously and be prepared to instantly use the weapon in your defense. Use the same sort of tactical commands you would use if surprised by an aggressive animal, like a stray Rottweiler or black bear ("GET BACK. DROP THE KNIFE. TURN AROUND.") Be noisy, aggressive, and insistant. Know the exits and go that way, keeping your eyes on the BG, don't get within touching range. Be aware of your six, BG might have buddies sneaking up on you.
If blocked in and BG with knife won't let you out, that is threat of death or serious bodily injury to you AFAIK. If BG continues to be aggressive in the face of an armed target use whatever force is necessary to end the threat.
Oh yeah, and PRACTICE with your CCW. Practice often. 100 rds per month is the bare minimum and I personally do at least 5 times that.
Practice with multiple targets at or near to 20' away, all the way to 6' away if your range allows it.
It's been my experience that there are types of BG's in this scenario: Bullys, Real Criminals and Predators.
Bullys are the guys who beat the littler kids up in school and took their lunch money. As adults they have realized that people would still rather give up their valuables in the face of a threat than risking any violence. Most of these guys talk tough, show a knife, act badass, and run like little b*tches when you draw on them. They have discovered that it is easy to take when people will quickly give. They seek easy targets of opportunity and can be avoided by staying alert. They will also go from runaway crybaby to stab you in the back because their pride has been hurt so stay alert.
Real Criminals are guys who have made a conscious decision to rob and steal. They are "Career" guys. They are making a conscious investment of time to attain a return. They will use their weapon to gain their goal. They will kill if necessary but it is not their usual preferred ending since that means a murder charge if caught. Divert their attention and get the drop on them and they will leave the situation, because they know there are easier sheep to find. Never underestimate them because as soon as you think it's over and relax they try again. Often these guys get in real close and go for the "shock and awe" tactic, like sticking the knife right against your throat. A lot of crackheads start off as bullys and end up real criminals.
Predators are the guys who like to dominate other people. Robbing is just a side benefit, they enjoy forcing others to submit. These guys will kill or wound for the hell of it. Since they are armed and you aren't you are just prey. They are likely to take your money or valuables and still knife you anyway. Odds are if you give in they will think you even weaker and thus be more likely to attack you. Odds are you are going to be fighting for your life anyway, might as well get that gun out and save your life now. A lot of predator types will be meth or coke users and that makes reasoning or dominating the situation unstable. These guys will probably just attack anyway.
He should have listened no money! 
