Concealed weapon carriers or other reasonably responsible, conscientious citizens are going to turn into whatever they turn into when adrenaline flows. People can become heroic and selfless when this happens, they can turn into gibbering masses, or they can do stupid things like fire their weapons at young [insert ethnicity here] boys who happen to walk by while wearing headphones and not realizing what danger they're in. This is one reason why police kill so many people wrongfully - and they are definitely trained and supposedly responsible.
If you have a way to react from a distance with deadly force to a situation that you don't necessarily fully understand but you see as an imminent danger because of the part of it you have seen (and not necessarily fully understood) you kill people. Right or wrong, the decision is made in a flash of adrenaline fueled "judgement" and it's permanent if you croak the guy(s).
Take away the possibility of instant, distant, deadly force reaction and you get harmless shouting or maybe some fists flying. Probably nobody dies.
This is just an example I found. A single Google search for "wrongful death weapon" resulted in 664,000 results in 0.71 seconds.
My cousin Joe's undoubtedly tidy and wholesome residential neighborhood in Utah is unfortunately ripe for a killing. They've been seeing a rise in burglary there recently, and everyone is worried they'll be next. I bet a lot of his neighbors have guns. They'll shoot some guy who's chasing his dog into their back yard or whose three year old is hiding behind a bush next door or something. And that will be that. He'll be dead, and nobody can reanimate him after the responsible citizen's snap judgement and use of deadly force took away his chance to explain his peaceful intentions.
The idea that arming everyone will make everyone safe is ridiculous and I can prove it. Several US Presidents have been shot while they were surrounded by a team of the best armed and trained protection specialists the world has ever seen who were absolutely focused on their task and not distracted by carrying their groceries or children or looking at the scenery as a normal person would be. Despite what the NRA tells its members to believe, there's simply no credible justification for saying that being armed yourself or in the company of armed people prevents a determined gunman from killing.