If the massacre in Maine had been the first, there might be some understanding of how it happened. If there’d been no Columbine two and a half decades earlier. If no one had shot and killed four people further down Interstate 295 in Bowdoin and Yarmouth, six months earlier. But, not a peaceful year has gone by since the Columbine massacre. Every one of the last 25 years has been cratered with gun violence and the willful destruction of human life.