I go to that Market Basket weekly and have been specifically looking for people open carrying there. No luck, I'm starting to think Less may be seeing things.
As far as the good guy stopping a bad guy thing. It happens much more than you or I are aware of due to the news outlets not reporting it as it doesn't fit their narrative.
As far as the 1 to 100 thing.... here is another mass shooting that was stopped.
https://wearechange.org/law-abiding-...mass-shooting/
Not the appropriate venue to be discussing this, but it's here until it isn't.