A North Carolina man will spend the rest of his life behind bars for the murder of his girlfriend”s 15-year-old son, whose head he repeatedly banged against the floor until he died — while the victim’s younger sister watched.

Last week, Carroll was convicted of first-degree murder and two counts of felony child abuse concerning the death of Casey Johnson in Rockingham, located about 70 miles southeast of Charlotte. The court has sentenced him to life without the possibility of parole, ensuring he spends the remainder of his life behind bars.

“I cannot adequately express the horrors these children experienced at the hands of this defendant,” Richmond County District Attorney Jamie Adams said in a press release. “As a career prosecutor, I have never encountered a case like this one. It has forever changed these children, the jurors, court personnel and this community. These children expressed relief that the person responsible for killing their brother has been held accountable.”

Casey’s mother, Michelle Johnson, initially admitted to injuring her son on Jan. 20, 2021, prosecutors acknowledged, but they showed jurors a video of Carroll coaching his girlfriend on what to say so their stories could match, according to a courtroom report from the Richmond Observer. Johnson was initially facing murder charges but those charges were dropped in favor of accessory after the fact and felony child abuse. She has yet to be sentenced.

A child abuse expert likened Casey’s injuries to a car accident, local ABC affiliate WSOC reported. Carroll also reportedly subjected Casey as well as his two younger sisters to sleep and food deprivation, beatings and waterboarding for two years.

During her closing arguments, Adams said much of what the jurors had witnessed was awful.

“A lot of what you’ve seen, you’re not going to be able to unsee,” she reportedly said.

Before sentencing, one of Casey’s sisters addressed the court.

“I struggle with words to say,” she said, according to the Observer. “Joe made us so weak so that we couldn’t fight back.”

She said Carroll “took my family and ripped it into shreds.”

The two sisters’ aunt and uncle have since taken custody of them. Their aunt said she believes Casey would be pleased with the verdict because his sisters are now safe.

“I think, because [Casey] was such a protector of his sisters, that knowing how they are right now, and how safe and loved and protected they are … that it wasn’t for nothing and he got his sisters out of there,” Jennifer Jefferson said.

As for Carroll, he got exactly what he deserved.

“You are proving exactly who you are,” she said.