Joseph Horner pleaded not guilty after prosecutors said Victoria Castle was attacked inside a North Massapequa home.
MASSAPEQUA, NY — A Long Island elementary school music teacher has been charged with second-degree murder after prosecutors said he strangled his 25-year-old sister-in-law Monday morning inside a North Massapequa home where both lived in separate apartments.
Joseph Horner, 27, is accused in the death of Victoria Castle, a Stony Brook University doctoral student whose family wept in court as the case was described by prosecutors. Horner pleaded not guilty and was ordered held without bail. The charge carries a possible sentence of 25 years to life in prison if he is convicted.
Nassau County police said the case began at 8:44 a.m. Monday, when Horner called 911 from a split-level house on North Oak Street. Detective Lieutenant Daniel Steller of the Nassau County Police Department said the caller asked for police and an ambulance “for a deceased female.” Officers arrived and found Horner sitting outside the home. Police said they then found Castle unresponsive in the first-floor apartment, gave medical aid and took her to a hospital. She was pronounced dead at 9:25 a.m. Investigators said her injuries and the scene led them to believe she had been strangled.
Prosecutors said Horner lived with his wife in an upstairs apartment at the same address, while Castle lived in the downstairs apartment. They said Horner asked Castle to come upstairs to help him move a piano. Once she was there, prosecutors said, he attacked her from behind and placed her in a chokehold until she lost consciousness. Prosecutors also alleged Horner sexually abused Castle after the attack, changed his clothes and then called police. Authorities have not said whether additional charges are expected. Police said Horner’s wife, who had been married to him for three years, was away on a bachelorette trip at the time.
Police said Horner had known Castle since 2016, when he first met the woman who later became his wife. Prosecutors said he told investigators he had been interested in Castle for years. Steller said police believe Horner acted alone, and authorities said no one involved had a prior criminal record. The case drew a large emergency response Monday in the residential Massapequa neighborhood, where officers, detectives and medical personnel gathered around the North Oak Street home. Steller said there had been “much fear and confusion” in the community after the response, but police said they did not believe there was any wider threat.
Castle was described by Stony Brook University as a valued member of its campus community. University officials said they were deeply saddened by her death and extended condolences to her family, friends, classmates and faculty mentors. In court, members of Castle’s family cried and embraced as Horner appeared before a judge. Horner’s family also attended the proceeding but did not comment publicly on the allegations. The killing stunned neighbors who said they did not know much about the people who lived in the house but were shaken by the police presence and the details that later emerged.
Horner worked as a music teacher in the Oceanside School District. The district said he was placed on administrative leave effective immediately pending further review. Officials said they had no further information to release. Police said the case had no connection to the school district. Horner’s defense attorney, Gregory Grizopoulos, said the accusations did not match how Horner was known by people around him. “He’s an Oceanside teacher, he’s tenured, he’s very well loved by his students and his colleagues,” Grizopoulos said. The attorney said the defense would review the evidence as the case moves forward.
At arraignment, Horner signed an order of protection requiring him to stay away from his wife. Prosecutors said the investigation remains active, including the review of statements, physical evidence and the final medical findings in Castle’s death. Police have not released a full autopsy report. Authorities have also not detailed whether forensic testing was completed or whether surveillance footage, phone records or other records are part of the case. The next steps are expected to include further court appearances and grand jury review, unless the case proceeds through another procedural route.
Neighbors on and near North Oak Street said the block was unsettled by the sudden arrival of police and emergency vehicles. One neighbor, Marguerite Defillipis, said the situation was frightening because it happened so close to home. “It’s scary, it’s very upsetting,” she said. The home remained the center of attention as investigators worked through the timeline. Castle’s death also spread grief beyond the neighborhood, reaching the Stony Brook campus and the Oceanside school community, where officials moved quickly to separate Horner from his teaching post while the criminal case proceeds.
Horner remained held without bail as of July 1. Police said Castle’s death is being investigated as a homicide, and prosecutors are expected to continue presenting the case in Nassau County court.
Author note: Last updated July 1, 2026.