This is just another false argument that doesn't stack up. The number of times a member of the public has stopped a mass shooting because they themselves were armed is so infinitesimal compared to the volume of mass shootings in the US that you can hardly call it a number.
This link, which is supportive, can still only cite 24 occasions in 30 years where an armed civilian has ended or prevented a mass shooting.
http://memepoliceman.com/list-of-mas...med-civilians/
Compare that to the 1,624 mass shootings that there were in just the last 5 years!
https://www.theguardian.com/us-news/...s-gun-violence
I don't know how many mass shootings there have been in the last 30 years, but if you extrapolate from the last 5 you would get something like 9,700.
24 is 0.2% so a educated estimate of how many mass shootings have been stopped by armed civilians is a whopping 0.2%
The reasons are obvious:
- Most people (even if they have a licence to carry a gun/own a gun) don't take them to church, cinema, school, concert etc.
- Even if they did have a gun on them, the panic and confusion would probably prevent them from pinpointing the shooter
- the shooter may have an AR15 or other automatic weapon and the civilian just a hand gun
- Joe public is generally not Dirty Harry, and if someone is shooting, 99% of people, even if they have a gun, would not run towards the gunfire.