The convicted father of the Oxford High School shooter said in jailhouse phone calls that he wanted to ruin the prosecutor in the case against him and that she would be going to hell soon, sources confirmed.

James Crumbley made the comments to his sister while his case was pending, the sources close to the Oakland County Prosecutor’s Office confirmed.

The new details were first reported Monday by the Detroit Free Press.

A Michigan jury last week found Crumbley guilty on four counts of involuntary manslaughter for the shooting his son carried out, killing four classmates.

James Crumbley and his wife, Jennifer Crumbley, who was convicted on the same charges at a separate trial in February, are the first parents in America to be charged for a school shooting committed by their child.

James Crumbley allegedly told his sister that he was going to make it his goal in life to destroy Oakland County Prosecutor Karen McDonald, saying that she was going to hell soon, that she better be scared and that she was done, the sources confirmed.

“There’s a disagreement about what was said and the nature of that stuff,” Crumbley’s defense attorney, Mariell Lehman, said Monday, declining to expand on her characterization of Crumbley’s conversations and adding that lawyers on each side agreed to try to keep it out of the media.

Lehman declined to comment further after NBC News confirmed the details of what Crumbley was alleged to have told his sister.

Asked about the threats Friday, McDonald said that “he made a lot of threats” but that she didn’t want to elaborate because she didn’t want to give him more attention.

“I just don’t think it’s important to talk about,” McDonald said then.

Word of the alleged threatening statements first emerged publicly in the middle of Crumbley’s trial. On March 7, the judge signed an order after the prosecution and defense attorneys reached an agreement to restrict his jail communications.

For the rest of the trial, Crumbley could talk only to his lawyer and legitimate clergy and do research to help his defense — but prosecutor David Williams said in court that the restrictions could lift after a verdict was reached.

The Oakland County Sheriff’s Office said at the time that Crumbley’s jailhouse communications had been limited “due to threatening statements.” Contacted Monday, the office said it had nothing further to add.

While the sources wouldn’t specify the frequency or exactly how many threats Crumbley allegedly made, they confirmed there were multiple ones in 2022, 2023 and as recently as January, before the parents’ trials began.

Ethan Crumbley killed four students — Madisyn Baldwin, 17; Tate Myre, 16; Hana St. Juliana, 14; and Justin Shilling, 17 — and wounded seven other people when he opened fire with a handgun on Nov. 30, 2021.

His father had bought the Sig Sauer 9 mm handgun he used days before, and prosecutors say it wasn’t kept secured. McDonald last week called the facts “egregious” and said that the shooting was foreseeable and that the parents could have prevented it “with just the smallest of efforts.”

At trial, school staff members testified that both Crumbley parents were called to the school the day of the shooting about a drawing their son had made depicting a gun and a person who had been shot. Neither of them told staff members he had access to a weapon, and they said they couldn’t take him home, citing work.

James Crumbley’s defense maintains he had no way of predicting that his son would start shooting hours later.

“He wished that he had taken his son home that day. If he had known what was going to happen, he would have made different decisions,” Lehman said Monday, adding that Crumbley feels terrible about what happened to the families.

James and Jennifer Crumbley are scheduled to be sentenced April 9. It is the first time the parents — who can’t communicate with each other from jail — could see each other since they attended joint hearings together before their trials were separated. They each face a maximum of 15 years in prison.