Photos: NYPD mourns Officer Wenjian Liu

Officers carry the casket of NYPD Officer Wenjian Liu from his funeral in Brooklyn on Jan. 4.   (Carolyn Cole / Los Angeles Times)

The hearse carrying NYPD Officer Wenjian Liu leaves his funeral in Brooklyn on Jan. 4.   (Carolyn Cole / Los Angeles Times)

Officers turn their backs on New York Mayor Bill de Blasio, seen on a large monitor outside the funeral in Brooklyn.   (Carolyn Cole / Los Angeles Times)

Pei Xia Chen, widow of Officer Wenjian Liu, holds the flag given to her at the end of his funeral.  (Carolyn Cole / Los Angeles Times)

A sea of uniformed officers crowds around a Brooklyn funeral home to honor Wenjian Liu, 32, killed with partner Rafael Ramos, 40, on Dec. 20.  (Carolyn Cole / Los Angeles Times)

Police officers leave the funeral of Wenjian Liu.  (Carolyn Cole / Los Angeles Times)

Thousands gathered in Brooklyn to honor Wenjian Liu.  (Carolyn Cole / Los Angeles Times)

New York Police Commissioner Bill Bratton attends the funeral of Officer Wenjian Liu.  (Carolyn Cole / Los Angeles Times)

New York Mayor Bill de Blasio, center, walks with his wife, Chirlane McCray, to attend the funeral for Officer Wenjian Liu.  (Carolyn Cole / Los Angeles Times)

During the funeral for New York Police Department officer Wenjian Liu, police officers turn their back on New York City mayor Bill de Blasio in Brooklyn.  (Carolyn Cole / Los Angeles Times)

The sentiments of some are shown during the funeral of New York Police Department officer Wenjian Liu.  (Carolyn Cole / Los Angeles Times)

A New York Police Department officer turns his back on Mayor Bil de Blasio during Wenjian Liu’s funeral.  (Carolyn Cole / Los Angeles Times)