LOGAN, Utah (AP) — A Utah man pleaded guilty Tuesday to killing and sexually assaulting his 5-year-old niece whose disappearance earlier this year triggered a massive search and widespread concern in a picturesque mountain valley community.

Alex Whipple, 21, entered his guilty pleas to murder, kidnapping and rape Tuesday as part of the agreement that dismissed charges of obstruction of justice and desecration of a body.

Police say he killed Elizabeth “Lizzy” Shelley on May 25, after his sister let him spend the night at the family home. Lizzy was missing for five days before her body was found in a heavily wooded area less than a block from her home.

Prosecutors had previously agreed not to pursue the death penalty after Whipple gave his lawyer a map of where to find Lizzy’s body.

Cache County Attorney James Swink said Lizzy died after Whipple stabbed her in the back with a knife he took from his sister’s home in Logan, Utah, The Salt Lake Tribune reports.

Whipple hung his head as Swink spoke about the details of the crime and said “guilty” as each count was read.

His attorney, Shannon Demler, said there’s no excuse for his client’s actions, but that mental health issues played a factor. Demler told the Tribune that he plans to speak more about Whipple’s mental health at the sentencing hearing, though he accepts he’s facing a lengthy prison stay.

“He’s known all along from the very beginning that what he did was terribly wrong,” Demler said, “and that he was going to face prison time.”

During an interview with police after he was arrested in May, Whipple told detectives that alcohol made him “black out” and that he sometimes did “criminal things” while blacked out, authorities have said.

Lizzy’s aunt, Liesel Merrill, said after the hearing that her family misses her dearly.

“We are hopeful that the criminal case can be resolved quickly so that we can continue to grieve without the worry of court hearings,” she said. “We would like to remind everyone that Lizzy was about kindness, happiness and looking for butterflies and rainbows.”

Whipple is scheduled to be sentenced Sept. 24.