From a moral standpoint, the right thing to do is for the armed bystander to intervene, to save lives. But from a legal standpoint, the basis of being armed is personal self defense. Every armed citizen is not a substitute, amateur, self-appointed policeman. As laudable as this person's actions were, if as a society we go down that road, it will ultimately lead to chaos.
And this armed bystander was lucky. In a similar situation, he could have made a mistake, an innocent person could have been shot, and then he could be subject to legal liability. If you're going to intervene, you damn well better be sure you are shooting the right person. The police have legal protections, for their actions, that ordinary citizens do not.
None of this is correct or accurate.
From a legal standpoint, defense of others absolutely is justifiable in plenty of jurisdictions, mine included.
For example:
https://www.azleg.gov/ars/13/00411.htm
Then there's the second ammendment, which mentions self-defense exactly zero times. Doesn't even insinuate it. Not even a little bit.
It does, however, seem to indicate that an armed citizenry is necessary for the security of the nation.
In other words, the use of arms is justified as a means of protecting our countrymen.
The idea that armed citizens standing up & doing the right thing will lead to chaos is nonsense.
How long have Americans been armed? Last time I checked it was always.
Have we decended into a chaos of our own making yet? How many CCW-holders do we read about daily shooting up schools, malls, or nightclubs?
How many mass killings have resulted from armed 'good guys' going into spray & pray mode and killing everyone in sight?
The increase in people interested in carrying guns for self-defense is a response to the chaos we're already living in. Not the cause of it.
People who realize the police will rarely be there for them when it matters in an increasingly violent world.
What's the cause of this chaos? What's the cause of the violence & disregard for human life that seems to be increasing at a rapid pace?
I won't pretend to have all the answers, but I'll tell you one thing:
A diverse nation filled with people who's only concern is looking out for #1 is a pretty big part of it.
People defending the weak & needy aren't the cause of chaos. They're the cure.
I'm so sick & tired of heros like these being treated like dolts too stupid to realize they're putting themselves in jeapordy. Saving your own butt at all costs is not an indicator of intelligence. It's an indicator of cowardice.