RIVERSIDE, CALIFORNIA — Prosecution testimony began Wednesday in the trial of a man accused of killing a 16-year-old Moreno Valley girl because she got him expelled from school and then hiding her body in the San Bernardino Mountains, where authorities have so far not found it.

Owen Skyler Shover, 23, of Hesperia, is charged with first-degree murder under special circumstances in the death of Aranda Briones in 2019.

The prosecution and defense made their opening statements on Tuesday, and Riverside County District Attorney Mike Hestrin, who is prosecuting the case himself, called the first witnesses to the Riverside Hall of Justice on Wednesday.

Shover is being held without bail at the Byrd Detention Center in Murrieta.

His brother, 27-year-old Gary Anthony Shover of Hesperia, admitted to being an accessory after the fact as part of a deal with prosecutors in March. He was originally charged with first-degree murder, but after a preliminary hearing in 2022, a judge dismissed the charge and found him only for aiding and abetting. He was sentenced to 12 months probation.

According to Hestrin’s trial report, Aranda and Shover attended Moreno Valley High School in the fall of 2017 and moved in the same circles.

The victim was a “troubled” teenager whose parents were absent. She had been adopted by her grandfather, Carl Horskotte, and had lived with him at his home on Via Vargas Drive since she was three years old, the summary states.

Hestrin said that on the morning of Nov. 7, 2017, Aranda decided to join her friends, including Shover, at Community Park instead of attending classes at Moreno Valley High School. A sheriff’s security officer searching for truants spotted the teens in the park and tried to make contact with them, at which point someone in the group yelled “Police!” and all of the teens fled in different directions. Shover had a small-caliber handgun with him and threw it at Aranda while yelling at her to hide it, according to court records.

The victim became frightened and immediately threw the gun into a sewer. However, the police officer caught her in the act and later arrested and questioned her along with school administrators. At that point, she admitted that Shover had the gun and gave it to her, Hestrin said.

The matter came before the local school board in February 2018, and the board voted to expel Aranda and Shover from Moreno Valley High. She was enrolled in a nearby high school while Shover moved out of his mother’s house in Moreno Valley, into his father’s house and attended a high school in Hesperia. But he was outraged by his expulsion and what he apparently perceived as a breach of trust by Aranda, the statement said.

Homicide detectives with the Riverside County Sheriff’s Department later discovered a series of Snapchat, Facebook and other conversations the defendant had between November 2018 and January 2019 in which he attempted to purchase a firearm, the summary states.

According to investigators, he finally received one.

On Jan. 12, 2019, Shover contacted Aranda via text message and invited her to accompany him the next day while he made drug deliveries and “robbed drug dealers,” the complaint states. She arranged to meet him at Bayside Park, and the two met shortly before 5 p.m. on Jan. 13, 2019. Hestrin claimed Aranda got into the defendant’s Nissan Versa as two of her friends watched and the two drove north toward Box Springs Mountain.

Within an hour, she posted several pictures on her social media accounts showing her and Shover in his car, expressing her joy at being with her “buddy” who let her do some of the driving, the letter said.

Through “pings” from cell towers, Moreno Valley’s citywide camera system and security cameras outside homes in the area, the occupants of the Nissan were tracked around Box Springs Mountain for about 20 minutes. According to court documents, the vehicle turned north toward San Bernardino, toward a mobile home park, just before 6 p.m.

On the way, Shover contacted his brother via Facebook Messenger and told him: “Be ready for tonight. Have shovels and lighter fluid ready,” the message said.

The defendant picked up Gary Shover from the trailer park and the two drove north on state routes 138 and 18 into the San Bernardino Mountains. Between 8:33 p.m. and 10:14 p.m., the defendant turned off his cellphone, rendering the signal unreadable. The phone turned back on after he reached his father’s house at 16210 Grevillea St., prosecutors said.

In the weeks that followed, when she did not return home, Aranda’s family and friends filed a complaint with the sheriff, believing she was the victim of a crime. The investigation was initially treated as a missing person investigation, but “became a murder investigation (because investigators) found extensive and compelling evidence that the defendant meticulously planned and executed Aranda’s murder,” Hestrin wrote.

Among the highlights was a search of the Nissan, during which the trunk was sprayed with the blood-detecting Luminol, which demonstrated “the possible presence of a significant amount of blood that had accumulated in the floor of the trunk under the carpet.”

DNA was recovered from the vehicle, and according to Hestrin, it was eventually determined to be a match to Aranda.

Neither Owen nor Gary Shover had any previous convictions.