ALBUQUERQUE, N.M. (AP) — A New Mexico man who was 15 when he killed his parents and three younger siblings is set to be released later this month on his 21st birthday, but a prosecutor filed a motion to keep him locked up until a court rules on an appeal of his juvenile sentence.

Nehemiah Griego is scheduled to be released on March 20 when he turns 21 as outlined under a 2016 Children's Court order, which found he had been receptive to treatment and could be sentenced as a juvenile.

In her filing Monday, prosecutor Michelle Pato of the Bernalillo County District Attorney's office cited "generalized" threats Griego allegedly made toward others in arguing that he posed a potential danger to the community if released. A state police investigation into the allegations earlier this year, however, did not uncover any direct, criminal threats made by Griego during his time in state custody, according to a state police spokeswoman.

Griego had told investigators that he believed the allegations of the threats had come from people who were scared of him and likely trying to block his release. He added that he has had virtually no communication with people outside of the treatment facility where he is being held, and that he does not intend to hurt anyone.

He also carries no resentment toward his family, he said.

"I've moved on," he said. "I want to just live my life and I want to be left alone."

Griego was 15 when authorities say he fatally shot his parents, and three younger siblings at their home south of Albuquerque in January 2013. Griego first shot his mother in her bed as she slept, then his 9-year-old brother, and then his two sisters, ages 5 and 2, according to Bernalillo County Sheriff's officials.

Hours later, his father returned home, and the teen — who had been waiting in a bathroom — ambushed him, authorities said. He spent much of the day following the early morning shooting at the Calvary Church, where his father had been a pastor.

He later told a deputy that he had anger issues and had been annoyed with his mother before carrying out the shootings, according to sheriff's documents.

His attorneys have maintained in his defense that he had been abused at home and likely suffered a traumatic brain injury as a result of beatings at the hands of father. On Tuesday, his attorney Stephen Taylor said he didn't believe the state or the district court had the authority to keep Griego in custody after his scheduled release date.

"I don't know that they have grounds or the district court has jurisdiction to even keep Nehemiah in jail," Taylor said.

Prosecutors had argued for Griego to be sentenced as an adult and sent to state prison after he pleaded guilty, saying that the crime was premeditated and that he has not expressed remorse for it. Pato again made those two points in her filing Monday.

She also said Griego's older sisters remained in fear for their safety based on his past acts and statements.

Both told state police that they had been aware of reported threats made by their younger brother, but that neither of them had been threatened directly. They did not testify at a hearing two years ago where Griego was found to have made progress toward rehabilitation.

Numerous Calvary Church members also spoke to state police during their investigation, but it did not appear the original source of the allegation was disclosed or identified in the documents.

The interviews for the state police investigation were conducted in January. It's not clear when the case was closed.

Griego told investigators that he had learned to work through his emotions. He had been diagnosed with schizoaffective disorder and post-traumatic stress disorder, but he said he no longer takes medication for either.

He planned to continue therapy after his release, he said.

"He told me there is nobody out there that is worth his time and that he does not want to start his time over, that it is pointless to start over (in prison)," wrote State Police Agent Marcus Lopez.