People are under a very wrong impression that "having a gun makes me safe." It so fucking does not.
If your firearm is in a backpack, you absolutely do not have time to retrieve it before an attacker is upon you. If you are holding the firearm in your hand, and your attacker is less than about 20 feet away from you, they can easily get the jump on you. If you have a gun, now any conflict situation you become a part of includes a gun. If you have a gun, there is now a chance that that gun could be used against you.