A Long Island elementary school music teacher allegedly strangled and sexually assaulted his sister-in-law after secretly lusting after her for nearly a decade — then called 911 and waited for police to arrive.
Story Snapshot
- Joseph Horner, 27, a tenured music teacher in the Oceanside School District, is charged with second-degree murder in the death of Victoria Cassell.
- Prosecutors say Horner lured Cassell upstairs to move a piano while his wife was away, then choked her until she went limp and sexually assaulted her.
- Investigators say Horner admitted he had been lusting after his sister-in-law since 2017 — nearly a decade of hidden obsession.
- Horner pleaded not guilty and was held without bail; the Oceanside School District placed him on administrative leave.
What Prosecutors Say Happened
Nassau County Assistant District Attorney Alexander DePalo laid out a chilling sequence of events in court. Prosecutors allege Horner used the excuse of moving a piano to get Cassell alone upstairs. Once there, he allegedly placed her in a chokehold without warning and held it until her body went limp. He then allegedly sexually assaulted her, changed his clothes, and called 911 himself before police arrived.
Investigators say Horner told them he had been lusting after Cassell since 2017. That admission gives prosecutors a clear motive — nearly nine years of obsession that allegedly turned deadly the moment his wife left town for a bachelorette party. Horner was arraigned on June 30, 2026, at First District Court in Nassau County, where he pleaded not guilty and was ordered held without bail.
A Trusted Teacher With a Hidden Side
Horner held a tenured position as an elementary school music teacher in the Oceanside School District on Long Island. Parents trusted him with their children every school day. After his arrest, the district placed him on administrative leave pending review — but issued no public statement about his background or fitness to work with children. That silence leaves parents with more questions than answers about how long warning signs may have gone unnoticed.
Victoria Cassell was a 25-year-old doctoral student described by those who knew her as deeply loved with her whole life ahead of her. She was family — Horner’s sister-in-law — which makes the alleged betrayal even more devastating. She had no reason to distrust the man her sibling married. She came to help move a piano and never came home.
What the Case Reveals About Trust and Accountability
This case is a stark reminder that danger does not always come from strangers. It can come from someone sitting at the family dinner table. Horner held a position of public trust — shaping young children in a school setting — while allegedly carrying a dark secret for years. The case raises hard questions about what warning signs, if any, existed and whether institutions like schools do enough to vet and monitor the people they employ long-term.
A New York elementary school music teacher has been charged with the murder of his sister-in-law. Joseph Horner, 27, is accused of strangling 25-year-old Victoria Castle in their shared multifamily home.https://t.co/b7hcMnKIwr#NYMurder #TeacherCharged #FamilyCrime #BreakingNews pic.twitter.com/02Gi4inPz0
— All the News (@allthe_dot_news) July 2, 2026
The trial process will determine guilt or innocence. Horner has pleaded not guilty, and a full jury has yet to weigh the evidence. Forensic findings, including autopsy results and any physical evidence from the scene, have not yet been made public. What is clear right now is that a young woman is dead, a family is shattered, and a community is asking how a trusted educator could allegedly lead such a double life.
Sources:
nypost.com, instagram.com, pdcn.org
