The family of a murdered Bronx auto body shop owner who was cooperating with authorities against drug dealers confronted his killers in court Tuesday, offering tearful statements about the impact of his 2016 strangulation with a zip tie — before a Manhattan judge hit each killer with two life sentences apiece.

The mother of slain Robert Bishun, 36 — who was kidnapped by Juan Rivera, 41, and Robert Pizarro, 39, during an attempted drug money robbery at Bishun’s shop — kept her eyes glued to Rivera at his sentencing in Manhattan federal court as she told him that her son’s death has “taken a piece of my heart” and devastated their family.

Sylvia Bishun noted that her son’s younger children still ask about their father, almost three years after he was killed.

“Your family can visit you,” she said, motioning to members of Rivera’s family who were seated in the courtroom. “But we all have to go to a tombstone.”

Still, she said, “being a Christian woman,” she has forgiven him for killing her son, a father of four, who was found dead in the backseat of his own BMW.

“Vengeance is not mine — vengeance is God’s,” Sylvia Bishun said.

Rivera, wearing a tan jail jumpsuit, looked back at the grieving mother without expression. He spoke only briefly when Judge Alison Nathan asked if he had anything to say for himself.

“I would like to maintain my innocence, that’s all,” Rivera said.

During the sentencing for Pizarro, which came later on Tuesday, he too proclaimed his innocence, turning to family members seated in the courtroom and raising his right hand.

“I did not commit this crime,” he said. “I did not commit this crime, my hand to God. You’re not getting justice here today.”

On the day of Robert Bishun’s death, in September 2016, Rivera and Pizarro burst into his shop brandishing firearms and zip-tying two hapless customers who ended up getting stuffed into the trunks of two cars being worked on at the shop.

The assailants were looking for narcotics proceeds, and Bishun, who had been a heroin dealer, told them that he was cooperating with the government.

“You’re a f—ing snitch?” Pizarro replied, according to court papers, at which point the assailants kidnapped Bishun from the shop.

Nathan cited the incident prior to giving both Rivera and Pizarro two life sentences plus an additional 14 years for Pizarro and an additional seven years for Rivera.

“A man deeply loved by his family was brutally, horrifically and senselessly murdered after he revealed to Mr. Rivera and his co-defendant during an attempted robbery that he is a government witness,” the judge said.

Both Rivera and Pizarro were convicted of kidnapping that resulted in death and with killing a government witness, which both carry mandatory minimum life sentences. They were also convicted of kidnapping conspiracy, robbery and gun charges.