Chapel Hill, N.C. — Adam Sapikowski pleaded guilty Friday to second-degree murder in the April 2005 shotgun slaying of his mother, and was sentenced to up to 25 years in prison.

The Chapel Hill teen already faces between 19 and 24½ years in prison for his father's death. Friday's sentence of 247 to 306 months will be served at the end the previous sentence.

Investigators said the bodies of James Sapikowski, 52, and Alison Powell Sapikowski, 49, had been in their Chapel Hill home for weeks before police discovered them wrapped in blankets behind a barricaded door on May 13, 2005.

Both had been shot several times at close range with a .410-gauge shotgun, police said.

Sapikowski claimed he killed his parents in self-defense. His attorneys said James Sapikowski had threatened his son with a bat and that physical and emotional abuse had provoked the shootings.

The teen also claimed that an argument over a girlfriend and grades led to the murders.

Orange County District Attorney Jim Woodall said Friday that a report card spattered with James Sapikowski's blood was found in the house.

The shotgun used in the slayings was found packed in a car in the garage, along with camping gear and other items that made it look like Adam Sapikowski intended to flee the area, Woodall said.

Sapikowski attended his junior prom after the slayings, neighbors told authorities that he hosted an after-prom party.

Woodall said the teen told anyone who asked about the strong odor in the house in subsequent days that some food had spoiled in the refrigerator.

Sapikowski's sister, half-brother and aunt read statements Friday before sentencing to express their grief over the two slayings.

"Since I've been deprived of my parents by Adam's actions, I define myself by one word: orphan," Lauren Sapikowski said. "There isn't a day that goes by that I'm not reminded of my being alone."

Chris Sapikowski choked back tears as he recalled his father playing basketball with him and his friends and teaching him life lessons along the way. He said he doesn't know how to explain to his young daughter why she never got to meet her grandfather.

"How could such a senseless act destroy two wonderful, giving and supportive people?" said Pamela Powell, Allison Sapikowski's sister. "We will be forever tormented by the cruel and senseless way that you left this world. There is a deep sadness that is beyond repair. We've lost a part of ourselves, and the pain is incredibly huge."

Adam Sapikowski rested his head on a table in the courtroom as he listened to his relatives. His attorney, Rosemary Godwin, rubbed his back to comfort him.

Last month, Sapikowski pleaded guilty to felony obstruction of justice and agreed to plead guilty to killing his parents. The plea was structured in parts so he would have a felony conviction on his record when he was sentenced for each killing, allowing Fox to impose a stiffer prison term, authorities said.

He has already spent nearly three years in jail.