I had a gunman open fire at my place of work a couple years ago, killing one and almost killing another. Luckily, I worked at a place that had A LOT of armed police officers. It took 7 officers, and about 85 shots, to take down this gunman. From my perspective, I was hiding in a bathroom with 6 other people, with all of us defenseless.
Immediately after, I wanted a gun. However, after reflecting and talking to a couple of different people with a variety of ideas, I've decided against it. I agree that it absolutely make a situation worse. When I was hiding in the bathroom, we had NOOOO idea how many gunmen there were. We had heard 1, 3 and 4. In that moment of chaos, there are a lot of unknowns. The fact that it took 7 armed police officers 85 shots to take down the gunman, I knew that if it was just me vs. him, I probably would not have taken him down, and would have run out of ammo, and found myself running.
Additionally, what if one of the 6 people I were hiding with had a gun? I know (not knowing how many gunmen there actually were), I would have been incredibly uneasy, and when people get uneasy in chaotic situations, bad things can happen.
Just some perspective. Not saying I'm right, just saying that I've been in this type of situation, and wanted to offer another view.