Valley man was behind murders of Fullerton couple he met in furry community and their friend, prosecutor says

A San Fernando Valley man masterminded the 2016 triple murders of a husband and wife he knew through the “furry community” and a friend staying at their Fullerton home after becoming obsessed with the couple’s teenage daughter, a prosecutor told jurors on Wednesday, Oct. 30.

Frank Felix, then 25 and a Sun Valley resident, had fallen in love with the 17-year-old before her mother and stepfather — Jennifer, 39, and Christopher Yost, 34 — ordered him to stay away from the family, Senior Deputy District Attorney Seton Hunt said during his opening statements in Orange County Superior Court.

Felix, Hunt alleged, teamed up with Joshua Acosta — a then-21-year-old Army mechanic — to carry out an ambush and the execution of the Yosts during the early morning hours of Sept. 24, 2016. Arthur “Billy” Boucher, a friend of the Yosts’ who was spending the night, was also shot and killed.

Two other children, 6 and 9, were in the home but not injured. In her testimony in Acosta’s trial, the girl said she let Acosta into the home, then waited in his truck with Felix. It’s unclear if she knew of the plan.

“(Felix) became despondent and angry and eventually formulated a plan,” the prosecutor told jurors. “(Felix and Acosta) determined they would solve the problem by saving the 17-year-old from the clutches of her mother and stepfather by murdering them.”

Felix’s attorney opted to not give his opening statements at the start of the trial, reserving the right to present them to the jury later in the proceedings.

Acosta — the shooter who claimed he thought he was “saving” the teen from being sexually abused — was convicted in 2018 of the special-circumstances killings and sentenced to life in prison without the possibility of parole. The then-17-year-old, who the authorities say left with the suspects, was granted immunity by prosecutors.

Felix, the Yosts and their teenage daughter were all furries, people who role play and dress up as animals and take on their personas. All four also knew Acosta, who was a “Brony,” a man who is a fan of the “My Little Pony” television series.

Hunt, the prosecutor, told jurors that Felix’s romantic relationship with the girl ended, at her parents’ insistence, months before the killing. Once after the breakup, Felix cut his arm in front of the girl, the prosecutor added.

Shortly before the slayings, Felix, in a message shown to jurors, wrote to an acquaintance: “I might be assisting someone in murder.” When the other person responded, “Don’t do it,” Felix replied he was just talking about an animal, the prosecutor said.

Felix purchased shotgun ammo, the prosecutor said, and along with Acosta bought earplugs and a bolt cutter, which Felix is accused of using to cut a security lock on his father’s shotgun.

Acosta shot Boucher in the head while he slept on a couch, Jennifer Yost between the eyes as she slept in her bedroom, and Christopher Yost as he tried to flee from the home.

The two younger children woke to find their parents dead. In a 911 call, one told a dispatcher: “My dad is outside in the backyard dead, my mom is in her bed dead.”

After identifying Acosta as a suspect, Fullerton detectives called authorities at Fort Irwin, where Acosta was stationed. Authorities at the base searched Acosta and found three shells that were later tied to the shotgun used in the killings.

“Three victims, three shotgun shells,” Hunt told jurors.

The girl testified during Acosta’s trial that she was molested by Christopher Yost, her stepfather, on a weekly basis when she was 7 to 15 and that Felix had “blackmailed” her into having sex with him by threatening to tell her mother about the alleged sexual abuse.

A prosecutor during the previous trial told jurors that there is likely no way that authorities will ever know if there was any truth to the sexual-assault allegations.

In an interview with police, Felix cited the abuse claim: “I knew she wouldn’t be safe if the parents weren’t killed.” But the prosecutor noted that Felix admitted he could have called police instead.

Acosta, in his own police interview, referred to the Yost family as a “festering wound” that he had “cauterized.” He said Boucher was “collateral damage.”

Felix told police he went along with Acosta because he thought Acosta would use unspecified “connections” with the Los Angeles Police Department against him, the prosecutor said.

Felix also told police that he knew the two younger children were going to be at the home, but they planned to make it look like a robbery and were going to leave food for them, the prosecutor said. Felix also acknowledged that he was aware that Boucher was staying at the home that night, the prosecutor noted, telling police, “So I already knew there was going to be a third body.”

Acosta’s defense attorney during the earlier trial argued that the then-17-year-old wanted her parents dead and manipulated Acosta. It it isn’t yet clear what Felix’s attorney plans to argue to the jury.

Felix faces three counts of murder and, if convicted as charged, life in prison without the possibility of parole.