Prosecutors said Joseph Horner attacked Victoria Castle after asking her to help move a piano.
MINEOLA, NY — A Long Island music teacher pleaded not guilty to murder after prosecutors said he strangled his sister-in-law Monday morning inside a North Massapequa home where both lived in separate apartments.
Joseph Horner, 27, was charged with second-degree murder in the death of Victoria Castle, 25, a Stony Brook University doctoral student. Nassau County officials said the case began as a 911 call from the same North Oak Street house where Castle was found not breathing. Prosecutors said Horner later told police he had been interested in Castle for years and acted while his wife was away.
Police and prosecutors said Horner lived with his wife in an upstairs apartment at the multi-family home, while Castle lived in a ground-floor unit. The attack happened Monday morning after Horner asked Castle to come upstairs to help him move a piano, officials said in court. Prosecutors said Horner attacked her from behind without warning and placed her in a chokehold until her body went limp. Nassau County police Detective Lt. Daniel Steller said a male caller requested police and an ambulance for a deceased woman at the home.
Officers arrived and found Horner sitting on the stoop, authorities said. Castle was found not breathing in the ground-floor apartment and was taken to a hospital, where she died. Prosecutors said Horner changed his clothes after the attack and called 911. They also said he sexually assaulted Castle after choking her. The exact full timeline between the alleged attack, the 911 call and the arrival of officers has not been released. Authorities have not said whether investigators recovered physical evidence from the apartment or whether additional charges could follow.
Castle was identified by police as the woman killed at the home. Reports described her as a Ph.D. student in geosciences at Stony Brook University. The killing shocked people who knew both families and the Oceanside school community, where Horner worked as a music teacher. Prosecutors said Horner had told investigators he had been interested in Castle since 2017. His wife was away on a trip when the killing happened, officials said. The home’s layout became central to the case because the suspect and victim lived near each other but in separate units.
Horner was arraigned Monday and pleaded not guilty. He was ordered held without bail, and a judge signed an order of protection requiring him to stay away from his wife. Defense attorney Gregory Grizopoulos said outside court that Horner had been married for three years and lived in the same house as Castle, who occupied another apartment. “What the motivation was and what the allegations are, we will figure it out as we move forward,” Grizopoulos said. The case is moving forward on a felony complaint, and prosecutors are expected to present evidence as the criminal process continues.
The Oceanside School District placed Horner on leave after the arrest. District officials said Nassau County authorities indicated the charges had no connection to the school district or its students. Neighbors and acquaintances described the allegations as difficult to process. One neighbor told reporters she did not know the family well but was stunned by the police response on North Oak Street. Others who knew Castle remembered her as intelligent and kind. The case drew wider attention because of Horner’s job as an elementary school music teacher and Castle’s academic work.
As of Wednesday, Horner remained in custody while Nassau County prosecutors continued the case. Authorities had announced a murder charge, but the investigation into the alleged sexual assault and the events inside the home was still ongoing.
Author note: Last updated July 1, 2026.