I'm seeing the Mr. Rogers quote floating around Facebook and couldn't agree more with the sentiment. Tragedies like this make us feel helpless, especially if we're far away from home. The smallest way to help is to remember the heroes of this event, not the villains.
As we recoil from the initial phase of shock, it's tempting to cope with this anger and grief by going on a witch-hunt. But please (and this extends to the media, too, since they are monitoring us through 3rd-party ads): Do not put a face to the insects behind the explosions. Do not ask why it happened, what drove them to it, whether their parents loved them or what hot-button disorder they may have had. Discussion is the source of their power.
The people whose lives we must follow in detail are the ones who helped in this tragedy. As Fred Rogers would say, "Find the helpers." Especially Carlos Arredondo, who can be seen in another photo circulating on Reddit as he holds a tourniquet for a runner whose legs were removed by the blast. (To avoid stirring up panic, I won't link to any fear-mongering news stories) What a bad-ass.
I ran out of eloquence. Here is a turtle eating mashed potatoes.