More than likely the shop is owned by an ex-cop and many of the local LEOs buy stuff there.
And everyone who buys guns there is either a CHL holder with an extensive background check or has gone through a FBI background check. A very dangerous place to be sure.
I trained troops in the Army and trained a lot of people in civilian life. All the people in my classes or the classes I've been to have been great people - doctors, dentists, nurses, lawyers, pastors, priests, moms, teachers, dads, cops, judges, elected officials, military, you name it. These are the kind of people who go to that shop. Awful people for sure.
Please note - I'm one of the folks who posted already that I wouldn't worry about the location of the gun shop - but fwiw, criminals and/or people who have dangerous plans do in fact sometimes buy guns at gun shops. Sometimes they purchase the gun under false pretenses (false id), sometimes the gun shop owners are less than thorough in requesting id/following up with background checks etc. It's certainly not the usual norm and it's certainly not most gun shops, but it does happen.
polarbear
It's also worth noting that while a lot of soldiers are awesome people, a lot of them were bullies to begin with, and too many of them are coming home with PTSD and other psychological problems. The same can be said for law enforcement officers. Yet these people often have guns, extensive gun training, and can pass a background check with flying colors. The recent spate of shootings on military bases says it all.
But then, the historical record tells us that the people who pose the greatest threat to kids in schools are other kids themselves. The children of responsible gun owners have access to guns in the home, and they typically know how to use them.
You can count me in the "don't worry about it" camp as well, but if you use terrible arguments to support the position, you're going to make people worry once they notice how terrible the arguments are.
An example of a good argument would be that the gun store operators and patrons themselves are heavily armed, trained, and often experienced, so an active shooter would be confronted by an armed response quicker than you could dial 9-1-1.
Another example of a good argument would be that a school shooter is highly unlikely to obtain the weapon at a store next door, so the existence of the store next door does not add any level of threat. Most school shootings are done by current or former students, and the firearms usually are obtained from the home or the home of another gun owner. Whether that gun owner obtains that firearm from a gun store next door, or 50 miles away, makes no difference.