A teenager accused of helping his ex-girlfriend kill and dismember a 16-year-old classmate pleaded guilty Thursday to murder.

Cory Gregory, 18, had led authorities to the girl's remains, which had been chopped up, burned and dumped in two counties, Rock Island County State's Attorney Jeff Terronez said.

The teenager also agreed to meet with Adrianne Reynolds' family and explain his role in her death.

"That goes a long way to show his remorse," Terronez said.

Prosecutors say Gregory and Sarah Kolb, 18, killed Reynolds in Kolb's car over their school lunch hour at a fast-food restaurant on Jan. 21, 2005, then took the body to Kolb's grandparents' farm and burned it.

The pair returned two days later and sawed the body into pieces, dumping some remains on the farm and burying the rest in Black Hawk State Park in Rock Island, according to prosecutors.

Gregory faces 20 to 40 years in prison at his sentencing July 10, plus two to five years for an earlier plea to concealing a homicide.

Kolb was convicted of murder at her second trial in February and faces more than 60 years in prison.

Prosecutors said Kolb was angry because Reynolds, who had recently moved to the state, was taking her friends and had shown interest in Kolb's boyfriend and Gregory.

Kolb said Gregory killed the girl. In her first trial, which ended in a mistrial, Kolb testified that Gregory strangled Reynolds, then hit Kolb in the face and threatened to kill her, her family and her cats if she reported the crime. She did not testify in her second trial, when the defense rested without presenting a case.

Gregory denied Kolb's account in a television interview.

Defense attorney Steve Hanna said Gregory agreed to the plea deal because the evidence against him was "overwhelming." Under the deal, approved less than a week before his murder trial was to begin, he will not face additional dismemberment charges that could have added 50 years to his sentence.

Gregory's mother wept as the plea was announced and left the courthouse without comment.

The victim's adoptive father, Tony Reynolds, said he asked for the meeting with Gregory.

"I guess I just want to know what happened, why," he said. He said he doesn't know yet what he will say to his daughter's killer.