Music Teacher Murders Sister-in-Law in Chilling House Attack

​A North Massapequa community is reeling after a local music teacher was arrested and charged with second-degree murder in the death of his 25-year-old sister-in-law.

​Joseph Horner, 27, an elementary school music teacher in the Oceanside School District, was taken into custody on Monday, June 29, following the discovery of Victoria Castle, a doctoral student at Stony Brook University, in her ground-floor apartment.

​According to the Nassau County District Attorney’s Office, the incident occurred while Horner’s wife was out of town attending a bachelorette party. Prosecutors allege that Horner, who lived in an upstairs unit of the same multi-family home on North Oak Street, lured Castle to his apartment under the pretense of asking for help moving a piano.

​Once inside, investigators claim Horner attacked the victim from behind, placing her in a fatal chokehold. Prosecutors further detailed allegations that Horner then sexually assaulted the victim. Shortly after the attack, at approximately 8:45 a.m., Horner contacted emergency services. He remained at the scene and admitted his actions to responding officers. Castle was rushed to a local hospital, where she was pronounced dead less than an hour later.

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​During his arraignment in First District Court in Hempstead on Tuesday, Horner pleaded not guilty to second-degree murder. He is currently being held without bail.

​The case has drawn significant attention due to the defendant’s position as a teacher and the disturbing nature of the allegations. Prosecutors revealed that Horner had allegedly harbored an obsession with Castle dating back to 2017, the year after they first met.

​The Oceanside School District confirmed that Horner has been placed on administrative leave. In a statement, Superintendent Phyllis Harrington acknowledged the gravity of the news, noting that the district was working closely with law enforcement.

​”These are very serious and disturbing allegations, and there’s a very stark contrast between the allegations and his beloved reputation that he had as a teacher,” said Horner’s defense attorney, Gregory Grizopoulos, who stated that his client’s family is devastated by both the loss of Victoria Castle and the charges against their son.

​The investigation is ongoing as authorities continue to process evidence. If convicted of second-degree murder, Horner faces a potential sentence of 25 years to life in prison.

​News 12 coverage of the arrest