Terrorists or those who run terrorist operations terrorize us for the enjoyment of the payoff. The payoff is witnessing the terror and despair evidenced by society at large. If they terrorized just those AT the terror event, it would be worthless.
The way to disrupt their enjoyment is obvious: by forgoing the all the news coverage and political jawboning and threats or revenge and remembrances which come afterward. In other words, by turning a situation like the recent terror attack on the Boston Marathon into a non-event or 9/11 into a nonevent.
It's contrary to our nature it seems, but it would work. It might not end every act of terror, but after a while it would assuredly cut their frequency way down,
There also seems to be a difference in the way we react to deaths caused by violence than to deaths caused by accident. I imagine that the explosion in Texas did a lot more damage and killed more people than in Boston and it would have been just as terrifying. It could be because one of them made us feel under attack and thats a scarier feeling.
The Texas explosion is an action (or so it seems) and accidents tend to lack intentionality. When an act is intentional, as in the Boston explosions, we want to know why someone felt a need to do that. If it turns out the Texas explosion was an act of terrorism or sabotage, we'll become more interested in it. Otherwise, it's just something sad and unfortunate that happened.
It may have something to do with the existence of a focal point for blame. When there is a specific perpetrator and the act is malicious, it enables the emotion of shock to be converted to anger, thus giving it an outlet for release.