If ever there was justification for this defensive gun use, then this would probably fit the bill.
Man shot after attacking ex-girlfriend
Note that Allen, the now deceased perpetrator, not only stabbed his ex-girlfriend, but forced his way into another man's home to do so while children were present. Pretty clear cut case of self defense. Yet, again, the police statement that they are unsure if any charges will be brought against the homeowner is troubling. There is no question that this was justified if the reported facts are true.
The lesson to be learned is that if you are forced to defend your life or the life of your loved ones, then do not expect to be treated like a hero. You will be most likely cuffed and possibly charged with a crime. That is how the New World Order works in this day and age.