Less than three years after Victoria Castle celebrated her sister's wedding with a glowing social media tribute to the groom, Nassau County prosecutors say that same man, 27-year-old music teacher Joseph Horner, strangled and sexually assaulted Castle inside the Long Island home they shared, then called 911 to report what he had done.
Horner was arrested at the scene in North Massapequa on June 29 and charged with second-degree murder on a felony complaint. He is being held without bail. Prosecutors told the court at his arraignment that his fixation on Castle stretched back more than a decade, a claim that reframes a family relationship most people around them apparently never questioned.
The case has shaken a suburban community and raised hard questions about how a man described by colleagues as "well-loved" could carry out the kind of act prosecutors have laid out in court filings.
Castle, a PhD student at Stony Brook University, lived in a ground-floor unit of a multi-family home in North Massapequa. Horner and his wife, Castle's sister, occupied the upstairs apartment. On the day of the alleged attack, Horner's wife was away on a bachelorette trip.
Prosecutors say Horner asked Castle to help him move a piano. Once she was in position, he allegedly attacked her from behind, placing her in a chokehold until she went limp. He then stripped her and raped her, the New York Post reported. Castle did not survive.
After the assault, Horner called 911. When detectives arrived, he admitted to committing the act. He was arrested for homicide at the scene.
At arraignment, prosecutors characterized Horner as having been "obsessed" with Castle for more than a decade and having "lusted over" her for nearly as long. Breitbart reported that prosecutors described the fixation as a "twisted fascination" dating back to when Horner first met both sisters in 2016.
After Horner married her sister, reportedly in 2023, Castle posted a Facebook message alongside a photo of the newlyweds sharing a post-nuptials kiss at their wedding venue.
"My sister, my person, my partner in chaos, is now married to one of the most wonderful people in the world. I love you both forever!"
That post, written in obvious warmth and trust, now stands as a grim artifact. Castle had no apparent idea that the man she was welcoming into her family had harbored what prosecutors describe as an obsessive fixation on her for years before the wedding, and would allegedly act on it less than three years later.
The timeline prosecutors have sketched is chilling in its patience. If their claims hold, Horner spent a decade watching, waiting, and ultimately marrying into the family of the woman he was fixated on, then struck when his wife left town.
Horner worked as a music teacher in the Oceanside School District on Long Island. Following his arrest, the district placed him on indefinite leave pending an investigation and issued a public statement.
"Nassau County officials indicated that these charges have no connection to the school district or its students. I recognize that this news is extremely disturbing, and I want to communicate with you directly."
The district's statement was careful to draw a line between Horner's employment and the charges. But the fact that a tenured public school teacher stands accused of this kind of act will not sit easily with parents in the district, regardless of where the crime allegedly took place.
Horner's defense attorney, Gregory Grizopoulos, pushed back on the prosecution's portrayal at arraignment. He told reporters that Horner had entered a not guilty plea and pointed to his client's professional standing.
"He's tenured. He's very well loved by his students and his colleagues. This seems to be allegations that are not very much in line with what the community, his friends, and his colleagues would believe."
That defense, essentially, "people liked him", will face the weight of Horner's own reported 911 call and his admission to detectives. A not guilty plea is every defendant's right. But the gap between the community's perception of Horner and what prosecutors say he did is itself part of the horror here.
People who knew both Horner and Castle have struggled publicly with the news. Sierra Catletti, a teacher who grew up close to Horner's family and now lives in Texas, posted online about the case.
"I grew up close to his family and am shocked and sickened by what he did to this beautiful girl. Never in a million years would I think he'd be capable of something like this. But guess you never really know someone."
Another person who attended college with Castle wrote on Instagram that she was "absolutely sick to my stomach," calling Castle "a beautiful soul and incredibly intelligent" and describing her death as "a heartbreaking tragedy."
Those reactions reflect what makes cases like this so deeply unsettling. Horner was not a stranger. He was family. He sat at holiday tables. He stood at the altar. And if prosecutors are right, he spent years concealing a predatory obsession behind the ordinary surface of a suburban life.
Several important questions remain open. The felony complaint charges Horner with second-degree murder, but it is unclear whether separate sexual assault charges have been filed or will follow. The specific court handling the case has not been publicly identified in available reporting. Whether Horner had any prior complaints, restraining orders, or documented incidents involving Castle, or anyone else, has not been disclosed.
Castle's sister, Horner's wife, has not been named publicly and has not made any statement. The depth of her knowledge, or lack of it, about her husband's alleged fixation on her own sister is a question that will hover over this case for a long time.
Horner's admission to detectives, as described by prosecutors, would seem to narrow the factual dispute considerably. But the legal process will play out on its own schedule. He has pleaded not guilty. He is being held without bail. The next steps belong to the Nassau County District Attorney's Office and the courts.
Victoria Castle was a young woman building a life, pursuing a doctorate at Stony Brook, living near family, trusting the people closest to her. She did what most people would do: she welcomed her sister's husband, praised him publicly, and shared a home with him. She had every reason to feel safe.
If the prosecution's account is accurate, that trust was weaponized. The piano was a lure. The bachelorette trip was an opening. And a decade of concealed obsession ended in the worst possible way, inside the walls of a home that was supposed to be shared in good faith.
Cases like this remind us that the most dangerous predators are not always strangers. Sometimes they are the people a family has already let inside.
