Last year's shooting at the Tree of Life synagogue was a stone dropping in water, creating concentric circles of grief. At the center were the survivors and the families of victims. Then came the first responders, and the local leaders who handled the overwhelming logistics involved in the aftermath. On and on: members of the Pittsburgh Jewish community. Pittsburghers writ large. American Jews. And, finally, the whole of the country, which saw the attack as part of the long list of mass shootings that have already happened this decade.