The medical examiner was able to determine the skull belonged to a female.

An Iowa man has been charged with first-degree murder after a teenager found a human skull belonging to a missing woman in a park.

The criminal complaint obtained by the BBC alleges that 23-year-old Nathan Gilmore killed 29-year-old Angela Bradbury in April 2021.

Three months after the alleged killing, in July 2021, a teenager discovered what appeared to be a woman's skull, "which had been placed on a stick," at the Greenbelt River Trail Park, south of Mitchell, Iowa, the complaint reads.

At the time, the medical examiner was able to determine the skull belonged to a female but unable to confirm an identity.

In February 2022, 10 months after Bradbury was allegedly killed, her family reported her missing to the Cerro Gordo County Sheriff's Office, according to the complaint. 

The family had allegedly not heard from Bradbury since April 2021.

DNA samples and dental records from her family helped authorities positively identify the skull as Bradbury.

Additional remains were found in April 2022 and Bradbury's death was ruled a homicide, according to the complaint.

Leading up to her death, authorities allege Bradbury met Gilmore at the Cerro County Court Jail on April 6, 2021. That day, the complaint states that Gilmore was at the jail for a court hearing while Bradbury was released on a charge of trespassing.

While questioning Gilmore on Friday in connection to Bradbury's death, authorities say his story changed multiple times, but that he did admit to picking up Bradbury near the jail on the day she was last seen.

Investigators said GPS records also showed Gilmore's Facebook account active on April 6, 2021 at the park where Bradbury's skull was found.

During a search of Gilmore's Osage, Iowa home, investigators allegedly discovered a whiteboard with the drawing of a "satanic goat's head in the shape of a pentagram."

The date Bradbury was allegedly killed and the coordinates of the park where her remains were found were also scribbled next to the drawing.

Authorities did not specify a motive in the killing or a cause of death.

Gilmore was arrested and is being held on a $1 million bond.

It was unclear if he entered a plea to the charge.

As of Wednesday, attorney information for Gilmore was unavailable according to the BBC.