Dozens of NYPD officers turned their backs Sunday as they watched Mayor Bill de Blasio eulogize an officer shot dead with his partner, repeating a stinging display of scorn for the mayor despite entreaties from the police commissioner not to do so.

The show of disrespect came outside the funeral home where Officer Wenjian Liu was remembered as an incarnation of the American dream: a man who had immigrated at age 12 and devoted himself to helping others in his adopted country. The gesture, among officers watching the mayor's speech on a screen, added to tensions between the mayor and rank-and-file police even as he sought to quiet them.

"As we start a new year, a year we're entering with hearts that are doubly heavy" from the loss of Officer Liu and his partner, Officer Rafael Ramos, de Blasio said. "Let us rededicate ourselves to those great New York traditions of mutual understanding and living in harmony. Let us move forward by strengthening the bonds that unite us, and let us work together to attain peace."

Police convened from around the country to mourn Liu, who was killed Dec. 20. Officer Lucas Grant of the Richmond County Sheriff's Office in Augusta, Georgia, said he came to Liu's funeral with about six other officers from neighboring departments "to support our family."