A 15-year-old South Jersey girl died from a deadly dose of heroin. Now, her dealer will spend 8 years in prison.

Burlington County drug dealer Austin Cooper was sentenced Thursday to eight years in prison for selling a deadly dose of heroin to 15-year-old Madison McDonald, who was found lifeless in her bedroom on the day after Christmas in 2017.

Beside her were lines of white powder, a rolled-up dollar bill, and a baggie with more heroin that prosecutors say was cut with fentanyl — a poisonous combination that Cooper sold to McDonald after researching how to create it and how to induce addiction in girls.

“She was my little baby. He took my little girl,” McDonald’s father, Stephen, said during tearful testimony Thursday as he urged the judge to impose a stiff sentence. “This guy, he’s just a menace to society.”

Stephen McDonald said his family has experienced a downward spiral after finding Madison unconscious in their Marlton home. She was flown to Children’s Hospital of Philadelphia, where she died two days later. Since then, he said, he has been depressed and is seeing a psychiatrist twice a month.

“I hope he lives in misery for the rest of his life,” the father said, glancing at Cooper, an acquaintance of his daughter, who sat emotionless throughout most of the hearing.

Cooper, 22, of Willingboro, later stood before Superior Court Judge Philip Haines, and apologized to the McDonald family and for bringing shame to his family. His voice cracked and he stopped briefly to compose his words.

“Madison was a beautiful girl,” Cooper told the judge as he stood beside his public defender, Anthony Aldorasi. “I never wanted this to happen, and I don’t want this to happen to anyone else.”

In April, Cooper entered an agreement with prosecutors in which he pleaded guilty to the first-degree crime of providing the drugs that caused Madison’s death in exchange for the eight-year sentence. Assistant Prosecutor Jeremy Lackey told the judge it was an appropriate sentence since the deal eliminated a trial that would have pained McDonald’s family.

The judge noted that Cooper had previous arrests, including one for drug possession, but no convictions. Two other offenses included criminal mischief and shoplifting. The judge also noted Cooper’s childhood, in which he was estranged from his mother, was abused and neglected by his father, and was twice placed in foster care.

In addition, the judge said, Cooper was addicted to the same drugs that killed Madison McDonald. He once attempted suicide by overdosing, Haines said, and had been placed in a residential treatment facility. He was also diagnosed with depression and anxiety.

The judge said Cooper preyed on the teen, taking her money as he peddled drugs.

After Madison’s death, Cooper showed a “shocking indifference to human life” when he posted Facebook messages that he “caught a dead body" and would need to keep selling drugs to pay for a lawyer, the judge said.

Cooper must serve 85 percent of his sentence before he can be paroled. Upon release, Cooper must serve five years of supervised release, and pay fines and fees.

Stephen McDonald said he approved of the plea offer because he did not want to risk a jury verdict of not guilty. Still, he said, he wished Cooper had been given a life sentence.

“My daughter got life,” the father said. “I’ll never celebrate another Christmas again. … I’ll never be the same again.”