New York (CNN)The ceremonial burning of paper money and the melodic sounds of Buddhist chants are marking a weekend of remembrance for the second police officer killed in an ambush by a lone gunman in December -- a sendoff that reflects the changing face of a department once known for its deep Irish and Italian roots. Under a mix of rain and snow, Det. Wenjian Liu was remembered Saturday at Aievoli Funeral Home in Brooklyn, where Mayor Bill de Blasio, Police Commissioner William Bratton, local officials and throngs of uniformed police officers and firefighters gathered at his wake in a sign of the diversity and unity of the nation's largest city.
@highlight
Fellow officers to say goodbye to Det. Wenjian Liu at a funeral home in Brooklyn on Sunday
@highlight
Don't carry out an "act of disrespect" against anyone, police commissioner says in memo
@highlight
At the funeral for Rafael Ramos, some officers turned their backs on Mayor Bill de Blasio
New York
On Sunday, a sea of dark blue drawn from the police forces of @placeholder and beyond is expected to find its way to the funeral home for Liu's funeral at 11 a.m.
Wenjian Liu
Wenjian Liu
On Sunday, a sea of dark blue drawn from the police forces of New York and beyond is expected to find its way to the funeral home for @placeholder's funeral at 11 a.m.
Bill de Blasio
Bill de Blasio
They had done it before, the night after the two men were shot dead in their car, when @placeholder entered the hospital to condemn the killing.
William Bratton
But for Sunday's funeral, @placeholder is putting his foot down at a potential repeat by some officers.
Wenjian Liu
Wenjian Liu
He expressly said there'd be no punishment for noncompliance at @placeholder's funeral but made sure the request was heard by all.
Rafael Ramos
Bratton promoted Liu and @placeholder to the rank of detective first grade during Ramos' funeral, to rousing applause.