Bones, honey...
that panic attack is the ultimate goal of terrorism (and this incident meets my definition of terrorism even tho it's only 1 person, acting alone) ... the bonus goal, is that now people fear each other more than ever, wondering who the next person will be to flip out and do something just as heinous. It's been on almost constantly in my house. It's been a feature of forums (and Facebook) too... and I'm sure the next person I chat with F2F will bring it up too. Even people I know who are rock-steady, optimistic, and usually carry-on... are talking about security and protection and contingency plans. THIS, by itself, scares me more than what happened in the theater.
SIGH!!!!!!!!
Fear is like rabies; extremely contagious and almost always fatal. BUT, the alternative - not being afraid - is to deny reality. Leaves a person wondering what to do... first: reassure yourself that you are not in immediate danger... and if you need to repeat a mantra, sit & breathe... just do it. Slow the brain down enough to catalog your surroundings and connect outward from your body to the seat you're on... the floor... the walls. Still OK. Keep going outward... until you can feel that you are in a safe zone and can move freely within it. You're OK; you're gonna be OK. It's OK.
And it's OK to be afraid, too. That's a normal, sane reaction. But the truth is that these kinds of events stick so dramatically in our collective memory we don't realize that they're relatively rare. It never seems (in the moment) that they're rare. Columbine! Is people's first association... but that was what? 10 years ago or more? Something like that anyway. These things don't happen every year; every month.
Hops is right - most of the time, most places - people are peaceful with each other and getting along (even when they have strong differences of opinion). Not everything is "political" either. Remember that the media are in the business of collecting "eyeballs"... attention... and for some reason right now, are trying to turn what is a horrible tragedy into a socio-political "issue" - which plays upon people's inner fears; could be another "threat". The media doesn't often challenge one's brain -- to think for oneself... and so overworks and manipulates our empathy... the only thing a person who is sensitive to these topics can do is TURN IT OFF.
I don't think there will be copycat incidents. HIGHLY unlikely, for a number of reasons.
I don't think you need to be suspicious of people you come in contact with -- there isn't going to be an epidemic of "crazy" all of a sudden. It's not the "zombie-pocalypse" starting. And the best thing you can do, is to simply go about your normal life with the same people you share it with. Some people deal with their fear, by talking it to death/boring/old news... some people are better off letting that all slide right on past them and while realizing it's a real thing... like a cesspool... you don't have to wade into it.
If you have to: stick your fingers in your ears and loudly chant: "la-la-la-la-la-la-la-la-la-la... I can't hear YOU..."