A judge sentenced Justin Robinson to 17 years behind bars on Thursday for the aggravated manslaughter of Autumn Pasquale, a 12-year-old girl whose life was cut short when her body was found stuffed into a recycling bin near the boy's Clayton home.

The 16-year-old, who — along with his older brother Donte was charged with Autumn's October murder — spoke only briefly inside the Gloucester County Justice Complex prior to Judge Walter Marshall accepting the plea deal Robinson struck with the Camden County Prosecutor's Office.

"I'm sorry and I never meant for this to happen," said Robinson, who showed little emotion during the sentencing.

Autumn went missing in late October last year, and after a massive days-long search through Clayton and surrounding towns, her body was found in a recycling container next door to the Robinson’s East Clayton Avenue house. Authorities said Autumn brought her white BMX bike to the boys' East Clayton Avenue home on Oct. 20, 2012 after Justin Robinson invited her there to work on her bike and exchange parts.

Justin Robinson, then 15, and his brother Donte, then 17, were both arrested and charged with murder. While Donte’s charges are still pending in juvenile court, Justin Robinson admitted last month to being the sole person responsible for luring Autumn to his house and strangling her to death.

As part of the plea agreement, Robinson will have to serve 85 percent of his term before being eligible for parole — about 14.5 years. Judge Walter Marshall recommended Robinson start his sentence in a youth corrections facility with the state. Marshall also described the crime as a "particularly cruel manner of death" which was something he weighed heavily in his decision.

During Thursday's sentencing, family and friends of Autumn — many who were hoping for a harsher sentence — packed one side of the courtroom. Tissues were passed around as the sentencing began. Occasionally, an outburst of emotion could be heard from someone on that side of the room.

Addressing the court, Autumn Pasquale's father Anthony Pasquale called Justin a "murderer who does not deserve to live."

The Robinson boys' mother spoke briefly during the hearing. When she spoke, a number of people on the other side of the room, including Tony Pasquale's lawyer Doug Long, abruptly left the room.

"Nobody knows what happened the day of the accident," she said, as the audience booed audibly. "The accident has been mischaracterized."

She added that she knows her son is "filled with remorse."

Throughout the two-hour-long hearing, part of the discussion focused on Justin's intellect. His lawyer said the teen boy has a low IQ, and had been previously diagnosed with attention deficit disorder (ADD) and post traumatic stress disorder (PTSD).

Had the case gone to trial, the lawyer said, it's possible his mental capacity would have been part of his defense.

"Although 17 years is not the longest sentence, it's a sentence that brings closure," Jaime Kaigh, an attorney for the Pasquale family said after the sentencing.

The prosecution publicly stated in August that “proving without reasonable doubt” that Robinson was the killer “would have been difficult” in court without the teenager’s admission of guilt. The crime scene lacked forensic evidence, they said.

Outside the courthouse, a crowd of protesters —some of them part of the more than 8,300 signatures on a petition arguing for a harsher sentence — gathered as they waited for word on the judge's decision.

"It's not enough time," said Jackie Budd, one of the protesters. "That was the face of innocence looking into the face of evil."

"To take an innocent child like that...it's uncalled for," said protester Florence Russell.

Donte’s murder charges are still pending in closed juvenile court.

Staff Writers Carly Romalino, Rebecca Forand and Jennica Torio contributed to this report.