Mourners sing the gospel song “This Little Light of Mine,” during a prayer vigil at the site where two police officers were fatally shot in the Brooklyn borough of New York December 21, 2014. New York Mayor Bill de Blasio faced the biggest crisis of his time in office on Sunday following the fatal shooting of two police officers, in an attack intended as retribution for recent U.S. police killings of unarmed black men. Police said the daylight Saturday shooting was the work of a 28-year-old black man who traveled from Baltimore that day after shooting and wounding his girlfriend, having warned on social media that he planned to be “putting wings on pigs,” using an anti-police slur. REUTERS/Stephanie Keith (UNITED STATES – Tags: POLITICS CRIME LAW CIVIL UNREST OBITUARY RELIGION)