FRESNO, Calif. (AP) — A 17-year-old boy charged with killing four members of a neighboring family in central California made his first appearance in court Thursday and entered the juvenile equivalent of a not-guilty plea.

The teenager, who was identified in juvenile court only by the initials R.I. because of his age, was ordered to remain in custody. If convicted of four murder charges, he would be held in juvenile hall until he turns 25.

Prosecutors have filed a motion asking that he be tried as an adult, with a possible sentence of life in prison without chance of parole.

The teen lived next door to the victims in the small town of Reedley, southwest of Fresno.

He is charged with killing 81-year-old Billy Bond; his son, 61-year-old Darrell Bond; granddaughter-in-law, Guadalupe Bond, 44; and grandson, Matthew Bond, 43.

The bodies of Billy Bond, Darrell Bond and Guadalupe Bond were found in the backyard of their home Saturday, including one that was buried in a shallow grave, police said. Matthew Bond’s body was found in the detached garage of the teenager’s home on Tuesday before he was arrested, authorities said.

Police haven’t released details of the killings but have said a safe inside the victims’ home that held guns and money had been forced open and emptied, suggesting a possible motive, The Fresno Bee reported.

Several of the teen’s relatives were in court for the hearing, including his mother. She and her boyfriend have been charged with being accessories after the fact to the killings and are free on bond.