A ruthless ex-con was arraigned on first-degree murder charges Tuesday in the traffic-stop shooting death of NYPD cop Jonathan Diller, Queens prosecutors said.

Guy Rivera, 34, was arraigned in Queens Supreme Court on an indictment charging him with first and second degree murder, attempted murder and six counts of criminal possession of a weapon as dozens of New Yorks Finest packed the courtroom — standing with the slain cop’s family.

“I hope that vicious, violent cop killer took a good look at the crowd in that courtroom because he’s going to see us every time he comes to court,” NYPD PBA President Patrick Hendry told reporters.

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“Great husband, great father, just an all around great family man who loved being a police officer and loves his family,” Hendry added.

Rivera is charged with shooting Diller, 31, during a routine traffic stop in Far Rockaway. Diller, the married father of a 1-year-old son, had gone to check on the suspicious-looking Kia Soul where Rivera and accused cohort Lindy Jones, who was behind the wheel, were sitting when Rivera opened fire and struck the young cop, according to police.

The bullet hit Diller below his bullet-proof vest, and he was pronounced dead at Jamaica Hospital.

Rivera already had 21 arrests on his rap sheet and had a shiv stashed in his rectum at the time of Diller’s shooting, with cops convinced the deadly duo was planning a heist.

Jones, 41, who had at least 14 prior busts, was arrested after the shooting and charged after cops found a second gun in the glove compartment.

At his funeral in Massapequa on March 30, Diller’s widow, Stephanie, called her slain husband a hero during a moving eulogy — with the couple’s young son, Ryan, nearby.

“My husband died a hero,” she said. But he also lived like one. Our world will never be the same, but I know I speak for everyone when I say I could not be more proud of him.”

Both Jones and Rivera are being held without bail.