Oceanside music teacher charged with murdering sister-in-law in North Massapequa home

An Oceanside elementary school music teacher strangled his sister-in-law in a North Massapequa apartment on Monday and now faces a second-degree charge, authorities said.

Joseph Horner, 27, pleaded not guilty Tuesday to murdering the 25-year-old woman, a Stony Brook University PhD student who was found not breathing by police Monday morning in a ground-floor apartment attached to a home on North Oak Street, police said.

Nassau County Assistant District Attorney Alexander DePalo said Horner, who lives in an upstairs apartment at the same home, asked the victim for help moving a piano before attacking her from behind, “without warning and unprovoked,” and placing her in a chokehold until she lost consciousness, according to Newsday‘s account of Horner’s arraignment.

DePalo further alleged that Horner then sexually abused the woman while she was passed out, changed his clothes, and called 911 at 8:45 a.m. to report she wasn’t breathing, waiting for police to arrive.

Officers performed CPR and rushed the woman to a local hospital, where she was pronounced dead at 9:25 a.m. Police did not give the victim’s name, only identifying her by age and as a Stony Brook student.

Horner was taken arrested at the scene and is being held without bail. He faces up to 25 years to life in prison if convicted.

Grizopoulos acknowledged the severity of what his client is accused of but stopped short of addressing the specifics, saying he had not yet reviewed the full body of evidence.

“The allegations are obviously very significant. They’re very severe. They’re very disturbing,” he said. “And that is very much in stark contrast to the reputation Joe Horner has as a teacher in the community.”

The attorney said his understanding of events is that Horner indeed called 911 and was sitting outside waiting for police to arrive — a detail he suggested could be relevant as the case unfolds.

“What he said and under what conditions he made any statements to the police, we don’t yet know,” Grizopoulos said.

On the living arrangement at the house, Grizopoulos said his understanding is that Horner and his wife of three years lived in an upstairs apartment while the victim lived alone in the downstairs unit, and that the families otherwise had a close relationship.

“They all had a great relationship, from my understanding,” he said.

Grizopoulos said he plans to investigate further as evidence is turned over by prosecutors in the coming weeks and months.

The investigation closed off the North Massapequa neighborhood for the entire day Monday. Police held a press briefing Tuesday morning to detail the case, though detectives have not disclosed a motive.

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Teacher since 2022

Horner has taught music at North Oceanside Road Elementary School #5 since 2022. Oceanside Superintendent of Schools Phyllis Harrington confirmed the arrest in a statement, saying Nassau County officials indicated the charges “have no connection to the school district or its students.” Horner has been placed on administrative leave effective immediately, pending further review, Harrington said.

“We understand that this news is deeply disturbing,” Harrington said. “The Oceanside School District is committed to maintaining a safe, professional, and trustworthy environment for our students, staff, and community. We stand by that commitment at all times.”

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