Joseph Horner, 27, was best known in his Long Island, New York, neighborhood as a tenured elementary school music teacher. Now, Horner is facing second-degree murder charges after his sister-in-law was found dead at their home.
According to People, prosecutors allege that Horner fatally strangled 25-year-old Victoria Castle on the morning of June 29. Horner and Castle reportedly lived in the same North Oak Street housing complex in North Massapequa. Horner and his wife lived in the upstairs unit, while Castle lived in a ground-floor apartment.
He allegedly changed his clothes
Prosecutors have also pointed to Horner’s alleged long-standing obsession with Castle as a possible motive. They claim Horner asked Castle to come upstairs to help him move a piano. Once she arrived, prosecutors allege he grabbed her from behind, placed her in a chokehold until she lost consciousness, and then sexually assaulted her.
Afterward, prosecutors say Horner called authorities himself. According to NBC New York, officers found him sitting on the front stoop waiting for them. By then, he had allegedly changed his clothes and was sitting with his head bowed.
Defense attorney Gregory Grizopoulos disputed the prosecution’s characterization of the case, saying, “My understanding is he was happily married for the past three years. He lived in the same house with his sister-in-law, who lived in another apartment.” He continued, “What the motivation was and what the allegations are, we will figure it out as we move forward.”
Neighbors said they were stunned by what happened. One resident, who said she did not know the family personally, remarked, “It’s scary, it’s very upsetting. We were frightened all day yesterday and last night because we live so close to the home.”
Castle was a Ph.D. student at Stony Brook University. While her family continues to process the tragedy, the university was among the first to release a statement. It read, in part, that it was “deeply saddened by the loss of Victoria Castle, a valued member of the Stony Brook University community. We extend our heartfelt condolences to her family, friends, classmates, faculty mentors, and all who knew and cared for her. During this difficult time, we are committed to supporting those across our community as they grieve.”
The Oceanside School District, where Horner works, has placed him on administrative leave pending the outcome of the case. Horner has pleaded not guilty to all charges. Prosecutors will now have to present evidence proving beyond a reasonable doubt that he committed the crimes alleged against him.
His wife wants him to stay away from her
Grizopoulos added, “He’s an Oceanside teacher, he’s tenured, he’s very well loved by his students and his colleagues. These allegations are not very in line with what his community, friends and family believe.”
The investigation remains ongoing. As prosecutors and the defense present their evidence in court, a clearer picture of what happened that day is expected to emerge. A key issue is likely to be the prosecution’s allegation that Horner had a long-standing obsession with Castle. If prosecutors intend to rely on that theory as a motive, they will likely need to present evidence supporting it before the jury.
Horner has also reportedly consented to an order of protection requiring him to stay away from his wife.
Published: Jul 1, 2026 02:44 pm