The funeral of NYPD Officer Wenjian Liu will be held Sunday in Brooklyn, New York, and police officers from across the nation have begun to arrive to pay their respects at Saturday’s viewing. Liu was killed execution-style in his patrol car Dec. 20 along with Officer Rafael Ramos, whose funeral was held last weekend.

Also appearing at today’s wake without incident was Mayor Bill de Blasio, on whom many officers turned their backs at the Ramos service. Police Commissioner Bill Bratton issued a memo reminding officers that the Liu funeral “is for grieving and not for grievances.”

Editor’s note: This post has been updated with additional tweets.