NEW YORK, NY - JANUARY 04: Hundreds of police officers from across the country turn their backs as New York Mayor Bill de Blasio speaks during the funeral of slain New York City Police Officer Wenjian Liu January 4, 2015 in New York City. Officers Wenjian Liu and Rafael Ramos were killed in an ambush while sitting in their patrol car last month on December 20. Thousands of fellow officers, family, friends and current FBI director is James Comey are expected at the Brooklyn funeral home for the service. Officer Ramos, was buried last week in Queens. (Photo by Spencer Platt/Getty Images)
