You may have already seen this, but it's worth repeating. Somebody posted it on Twitter after the tragedy in Boston yesterday - words of comfort from Fred Rogers, the beloved Mister Rogers of my children's childhood.
Blessings on the helpers, both those whose job it is to help in such events and those ordinary citizens who ran to help, instead of running for cover. They are our heroes. They are what gives us hope that the human race may actually survive, may actually be worth saving.