Had to chime in on this topic with my experience, yet at a very different shopping angle. I was on a shopping route when the shootings took place and in each of the 5 locations that I've visited, this was the primary subject of discussion. You just couldn't NOT talk about this.
Of course, I used this to my advantage while shopping. The safety of the targeted places on my route led to a very easy objection that I had to bring up. It all worked out. When I returned to my hotel later on that night, I was satisfied that I completed my route (amidst the circumstances) yet quite angry and full of sorrow. I wound up speaking with the front desk clerk for almost a half an hour (who was from a nearby suburb of Newtown, CT) about how we felt.