Full body armor including helmet and kneck guard and all legally bought guns in last few months. Someone armed wouldn't have helped much and no crime until he fired a shot...
Body armor is only good for so many rounds, and your average body armor that number is typically 3 to 5. When a bullet strikes a vest the material inside is "pulled" to the point of impact, that is by design and is part of the reason it can stop a round. After so many impacts the effectiveness of the material is compromised and ultimately it fails. A neck guard is only good for a single shot, maybe two because there is so much less material. Also the impact to the neck from the force alone is going to hurt like crazy.
Your average round in ball point FMJ will penetrate the average vest in 3 to 5 rounds. If the bullet is a 180 grain HP that number can be as low as 2, depending on the body armor (and a lot of other factors). Also remember even to a vest, it hurts. The shooter was undoubtedly close enough to the tear gas (it dissipates) that being struck by rounds even through a vest would cause pain and increased breathing, which would increase any effect of the gas.
For the past 14 years (8 more or less full time) I have worked with far more 12 year olds than I can count. I cannot think of one that I'd be comfortable with knowledge of the location of a handgun, ammunition, and encouragement to use them as needed.
Is your experience with them limited to any specific demographic or social level? I would imagine that the comfort would come with in home experience in that specific regard. For example my dad is a NRA certified firearms instructor, prior military and career law enforcement. He would never trust me around the keys to his car or liquor cabinet, but I started shooting when I was two and at 12 years old I had access to weapons for protection. I never laid a finger on a single one without permission, and was never tempted.
Most of it is about taking the mystery and fanfare out of it.