A Long Island music teacher allegedly raped and murdered his wife’s younger sister in their shared family home while his spouse attended a bachelorette party, according to Nassau County prosecutors who say the suspect harbored an obsessive fixation spanning more than a decade.

Decade-Long Obsession Ends In Violence

Joseph Horner, 27, faces second-degree murder charges after allegedly killing Victoria Castle, a doctoral student at Stony Brook University, on June 29 in their North Massapequa residence. Prosecutors revealed at his arraignment that Horner had been obsessed with his sister-in-law for over ten years before the brutal attack. The suspect lived in an upstairs apartment with his wife while Castle occupied the ground-floor unit of the multi-family dwelling.

Authorities say Horner lured Castle by requesting help moving a piano before attacking her from behind with a chokehold until she lost consciousness. After the assault, he contacted emergency services and remained at the scene, confessing to detectives upon their arrival. Police arrested him immediately for homicide, and he is being held without bail.

Dark Contrast To Wedding Day Tribute

The horrific crime stands in stark contrast to a Facebook post Castle wrote celebrating her sister’s marriage to Horner less than three years earlier. In the tribute accompanying a wedding photo, Castle called her accused killer one of the most wonderful people in the world and expressed eternal love for the couple. The message, which included a photo of the newlyweds kissing at their wedding venue, now carries haunting significance following her death.

Community Reaction And School Response

Friends and acquaintances expressed shock at the violent turn of events. One college friend described Castle as a beautiful soul and incredibly intelligent person, while a teacher familiar with Horner’s family said she never imagined he could commit such an act. The Oceanside School District, where Horner worked as a music teacher, placed him on indefinite leave pending investigation. District officials emphasized the charges have no connection to the school or its students, though they acknowledged the disturbing nature of the allegations. The case highlights the hidden dangers that can exist within seemingly normal family structures.