Installing metal detectors at movie theaters doesn't make sense -- there's no reason to think the next crazy gunman will choose a movie theater as his venue, and how effectively would a metal detector deter a lone gunman anyway? -- but understanding the reasons why the United States has so many gun deaths compared with other countries does. The particular motivations of alleged killer James Holmes aren't relevant -- the next gunman will have different motivations -- but the general state of mental health care in the United States is.Drawing the Wrong Lessons from Horrific Events - Bruce Schneier.
Even with this, the most important lesson of the Aurora massacre is how rare these events actually are. Our brains are primed to believe that movie theaters are more dangerous than they used to be, but they're not. The riskiest part of the evening is still the car ride to and from the movie theater, and even that's very safe.
But wear a seat belt all the same.
Drawing the Wrong Lessons from Horrific Events (en)
Bruce Schneier wrote this after the massacre in Aurora, but the lessons he draws are the same for the Sandy Hook killing spree : don't overeact for spectacular but rare events.