A 15-year-old boy was formally told Friday that he faces four counts of murder and three counts of sexual assault in the June death of a 10-year-old girl who was beaten and molested.

Kiaya Campbell’s body was discovered in a natural area in Thornton the day after she’d been reported missing.

Aidan Zellmer will be tried as an adult following a ruling earlier this week by Adams County District Judge Sharon D. Holbrook.

Zellmer appeared in court in green scrubs and a baby blue sweatshirt, his wrists and ankles shackled.

He spoke only five words, answering “yes” or “no” as Judge Holbrook asked him if he understood his rights, the process and whether he had any questions.

Zellmer faces multiple charges based on different legal theories:

■ First-degree murder – alleging that he killed her after deliberation.

■ First-degree murder – alleging that he killed a child under age 12 while in a position of trust.

■ First-degree murder – alleging that he killed her in the course of a sexual assault.

■ First-degree murder – alleging that he killed her in the course of committing sexual assault on a child.

■ Sexual assault – alleging that he committed sexual assault on a person younger than 15 and he was more than four years older than her and forced submission through force or violence.

■ Sexual assault – alleging that he committed sexual assault on a person younger than 15 and he was more than four years older than her and the victim suffered serious bodily injury.

■ Sexual assault – alleging that he committed sexual assault on a person younger than 15 and he was more than four years older than her and he applied force “to accomplish or facilitate the sexual contact.”

Campbell suffered multiple blunt force injuries to the head – some of which caused skull fractures – as well as wounds to several fingers, according to an autopsy report obtained by 9Wants to Know.

Two days after the girl’s body was discovered, Thornton police arrested Zellmer.

At the time Campbell was reported missing, her family told police that she and a 15-year-old boy had left a home in the 12400 block of Forest Drive in Thornton to walk to a nearby shopping center – then became separated in a rain storm. She was reported to have last been seen in the 12900 block of Colorado Boulevard.

The report sparked a massive search in the area for the girl – a search that ended late the next afternoon when a man discovered her body in a natural area roughly a mile east of the area where she was reported to have disappeared.

The autopsy report, released by Adams County Coroner Monica Broncucia-Jordan after an open records request by 9NEWS, details a horrific series of injuries – multiple open lacerations on the right side of the girl’s head, many directly connected to skull fractures.

It also described multiple injuries to her hands, including a broken finger and other contusions.

The report does not indicate what caused the wounds.

The next step will be a hearing that will lay the groundwork for the judge to determine whether Zellmer should be offered bail. The date for that hearing is expected to be set next week.

Contact 9NEWS reporter Kevin Vaughan with tips about this or any story: kevin.vaughan@9news.com or 303-871-1862.