Christopher Yost, 34, was murdered on September 24, 2016, in Fullerton, California. The killings happened in the early morning at the Yost family home; Christopher, his wife Jennifer Yost, and a friend, Arthur Billy Boucher, were shot dead there. A 21-year-old former Army mechanic, Joshua Acosta, carried out the shootings with a shotgun provided by Frank Felix, 25, who waited outside with the Yosts’ 17-year-old daughter, Katlynn Goodwill Yost.

The noise awakened Christopher, who attempted to flee and was shot in the head. Felix has been described as obsessed with Katlynn; both Acosta and Felix said they were trying to save her from alleged abuse by her parents, but those allegations remained unverified because the victims could not speak for themselves. Acosta was convicted of three counts of felony murder and given life without parole plus 75 years; Felix was convicted of special circumstances murder, with prosecutors portraying him as the mastermind.

Does anyone have information about the Yost family, Katlynn’s activities, or the people involved that could shed more light on what led up to this attack?