A missing person case in New Mexico turned into a murder investigation after police say a 15-year-old boy killed his 9-year-old cousin and abandoned her body.

>> Read more trending news

A woman called police Saturday to report her niece missing, local media reported, citing an Albuquerque police complaint.

The woman told police her niece had been staying at her house, KOAT-TV reported. She went to check on her niece and her 15-year-old son, but said she couldn't find the girl. The woman said she went driving and looking for her niece. When she returned, she said she found a note from her son, 15-year-old Jeremiah Morfin, that said he had gotten angry and killed the girl.

Morfin told police he “kind of lost it” and killed the girl, who was his cousin, the complaint said. Police said Morfin led them to the girl’s body, which he had left in an arroyo -- a dried-up creek bed.

There were signs of visible trauma to the girl’s head and chest, and signs she had been sexually assaulted, according to the complaint.

Morfin was arrested and charged with murder and tampering with evidence. He’s scheduled to appear Friday morning in District Court, where a judge will decide whether to keep him behind bars until trial or release him on his own recognizance.