NEW YORK—Fifth Avenue in Manhattan fell silent as pallbearers carried the flag-draped casket of NYPD officer Jason Rivera up the steps of St. Patrick’s Roman Catholic Cathedral on the morning of Jan. 27. The only notable sounds came from a police helicopter hovering above and “Amazing Grace” played on a single bagpipe. Hundreds of New York’s finest stood down the center of the avenue, wearing their class-A dress uniforms with white gloves, saluting their fallen brother. All had black, mourning bands across their shields. Rivera was shot and killed in the line of duty on Jan. 21, while responding to a domestic dispute involving a mother and her son in the Harlem section of Manhattan. A motorcycle escort preceded the hearse and a mounted unit was on hand. The NYPD had officers working the detail, including uniformed and plain-clothed cops, a K-9 unit, the Patrol Services Bureau, Emergency Services, and …