There are two major problems with attempting to answer this question:
the absence of a uniform consensus of what constitutes a mass shooting
the lack of a consistent primary source of data spanning all incidents – attempted or otherwise partially / fully committed
That is to say, databases that track mass shootings record and publish data in uniquified ...
There are several factors that make this a very difficult question to answer definitively.
What exactly is a "mass shooting"?
What exactly does it mean to stop a mass shooting?
How to account for mass shootings that are prevented by armed citizens, or even by the possibility that armed citizens will be present?
Should other similar violent crimes ...
Unfortunately, statistics based on actual events are not able to answer this question.
A working hypothesis is that a higher rate of gun ownership among targets will discourage potential shooters from trying. Similarly, easier access to guns will encourage potential shooters to try. The policy can clearly be counter-productive if only partially implemented, ...
From the details in the The Violence Project database. The following can be seen.
In six incidents, armed civilians were present at the location. (Armed
Police were present in 19 Incidents) out of 175 recorded incidents.
The average number of people who were killed and injured in these 175
incidents are 7.18 dead and 11.6 injured.
For shootings with an ...