Long Island Music Teacher Charged with Strangling and Sexually Assaulting Sister-in-Law

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Victoria Castle, a 25-year-old Ph.D. student at Stony Brook University, was found dead in her apartment on North Oak Street in Massapequa on Monday, June 29, 2026.

She was strangled, and according to police reports, the man now charged with her murder is her own brother-in-law, who told detectives he had been lusted on her for years.




Joseph Horner, 27, a local music teacher, lived with his wife in the second-floor apartment of the same house, while Castle occupied the unit below. 

According to prosecutors, it all began when Horner asked Castle for help in moving a piano. Then, without any warning, he attacked her from behind and put her in a chokehold, holding on until her body went limp. 

He is also accused of sexually assaulting her after the attack, changing his clothes, and then dialing 911 himself.

“The male caller requested police and an ambulance to this location for a deceased female,” said Detective Lieutenant Daniel Steller of the Nassau Police Department.

When officers arrived, they found Horner sitting on the front stoop waiting for them, so he was arrested and taken into custody. 

During the investigation, told police that he had been interested in his sister-in-law since 2017, and that he acted on those urges on that day because his wife—Castle’s sister—was away on a trip.

“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,” said Horner’s defense attorney, Gregory Grizopoulos. 

“What the motivation was and what the allegations are, we will figure it out as we move forward,” he added.




At his court appearance, Horner pleaded not guilty to second-degree murder and signed an order of protection that requires him to stay away from his wife. 

The Oceanside School District, where he worked as a music teacher, announced that he had been “placed on administrative leave effective immediately, pending further review.”

The killing has shaken people who live nearby, even those who did not know the family well. Neighbor Marguerite Defillipis described the fear that rippled through the area. 

“It’s scary, it’s very upsetting. We were frightened all day yesterday and last night cause we live so close to the home,” she said, as per NBC New York.

Castle’s family is now left to mourn a promising life cut short. Stony Brook University issued a statement saying they were devastated by the situation.  

“We are 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.”

Horner remains in custody as the investigation continues, and authorities have not pointed to any prior history of violence between him and Castle.

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