One theory of the right wing is that the more guns in the hands of potential victims, the less crime there will be overall. Now, I'm not an extremist, so I'm not going to discount the many times that people have used firearms to deter and/or prevent harm to themselves. Life being complex, I've found it difficult to quantify how often that is.
But the gun rights supporters refuse to deal with the reality that sometimes, the potential victim having a weapon actually increases the chance of them being attacked. This is because it can escalate a bad situation into an all-out crime scene.
A&E has has a terrific show called "The First 48", and on one of their episodes:
"left to burn/Trigger happy"
there is an example of a person being killed because he tried to get his weapon when he felt threatened. As he did so, the assailants murdered him, two people involved said they "simply" wanted to talk with the victim about his "attitude", but things changed when they felt threatened. Who knows what the actual truth is, but it's possible they wanted to intimidate and threaten the young man, and perhaps admonish him about some past incident, and then the situation became a mortal threat for all involved.
Now, this is the story of one of the admitted shooters; and it can be inferred that the victim had an illegal weapon; but the point still remains that had the victim been unarmed he could have possibly survived the encounter by genuflecting. That's speculation, but we do know in this case, it couldn't have been worse for him, either the same or better without a gun.