Manhattan funeral arrangements were announced Saturday for slain NYPD Officer Jason Rivera, as union leaders urged New Yorkers to attend the services to “send a message” to would-be killers in the city.

Rivera, who was gunned down during a domestic call Friday, will be mourned at St. Patrick’s Cathedral Thursday and Friday.

A wake will be held for the 22-year-old Washington Heights native from 1-8 p.m. at the massive Midtown house of worship on Jan. 27, followed by funeral services at 9 a.m. the following day, the NYPD said.

Rivera’s partner Wilbert Mora, 27, continued to fight for his life at Harlem Hospital Saturday after the two were ambushed by paroled felon Lashawn McNeil during a domestic call.

Rivera, a married father of one, had just joined the force 14 months ago. His death sent shockwaves across New York, with Mayor Eric Adams declaring the violence “an attack on our city.”

Pat Lynch, president of the Patrolmen’s Benevolent Association, the NYPD’s largest union, implored everyday New Yorkers to attend Rivera’s service on Friday to show solidarity with the department’s 36,000 uniformed members.

“It can’t be just us,” he said. “The streets can’t just be full of New York City police officers at this funeral. The public has to come. The public has to send a message to anyone that dares to harm a New York City police officer. Not here, not now, not today, not to us. We are humbly asking you to come out and help us.”

Many members of the public had already dug into their pockets to show their support for Rivera and Mora. An online fundraiser for their families had garnered $135,000 by Saturday night.