Ex-Athlete Found Dead in Cell After Brutal Delusional Slaying

The haunting saga of a former collegiate soccer player who brutally slaughtered his younger brother in a fit of psychotic delusions has reached a grim conclusion inside a New Jersey jail cell.

​Matthew Hertgen, 31, was discovered dead in his cell at the Mercer County Jail on May 8, 2026, officials from the Mercer County Prosecutor’s Office confirmed. While an autopsy is pending and an official cause of death has not been formally released, authorities are treating the incident as an apparent suicide.

​The grim discovery came on the exact same day that Hertgen’s highly publicized trial concluded. A New Jersey judge officially found him not criminally responsible for murder by reason of insanity, stemming from the horrific February 2025 slaying of his 26-year-old brother, Joseph Hertgen.

​A Night of Unspeakable Horror

​The tragedy unfolded on the night of February 22, 2025, inside a luxury residence at the Michelle Mews Apartments on Palmer Square, an upscale enclave near Princeton University.

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​According to police investigative reports and court records, Matthew Hertgen—who previously played soccer for Wesleyan University—had been battling profound mental health struggles for years. On the day of the murder, his eldest brother, David, noted that Matthew was severely despondent and experiencing terrifying hallucinations. Seeking to comfort him, David took Matthew grocery shopping before dropping him off at the Princeton apartment he shared with Joseph.

​Less than an hour later, the fragile peace shattered. Driven by severe psychotic delusions, Matthew launched a savage assault on Joseph. Investigators revealed that Matthew beat and stabbed his younger brother to death using knives and a golf club. The scene was described by responding officers as “gruesome” and “way overboard,” with Joseph suffering massive blunt-force trauma and extensive lacerations.

​In a chilling culmination of the attack, Matthew mutilated his brother’s body, ripping out one of Joseph’s eyeballs and consuming it. Before the frenzy ended, Matthew also inflicted blunt-force injuries on the family cat and set the animal on fire.

​At 11:16 p.m., Matthew placed a calm call to 911, reporting a fire and a dead body inside the home. When Princeton patrol officers arrived, Matthew opened the door with scratched, bloodied hands, telling officers he had fallen into a “fit of madness” about forty minutes prior. Joseph, an accomplished former University of Michigan star athlete and financial analyst for Locust Point Capital, was pronounced dead at the scene.

​Prophet Visions and Law and Order

​During the brief bench trial, forensic psychologist Dr. Gianni Pirelli testified that Hertgen suffered from severe schizophrenia and bipolar I disorder. Dr. Pirelli revealed that the defendant was plagued by “prophetic and divine visions” whenever he closed his eyes. At the time of the killing, Hertgen firmly believed the world was ending and that only a “sacrificial murder could save it.”

​Because of this profound break from reality, the court ruled that Hertgen could not be held criminally liable for the first-degree murder, weapons offenses, and animal cruelty charges brought against him.

​Hertgen’s vulnerability to self-harm was well-documented by the state. Court testimony from a March 2025 detention hearing revealed that he had previously attempted suicide inside the Mercer County Jail just a week after his initial arrest.

​Forgiveness Amidst Heartbreak

​Despite the unimaginable horror of the crime, Hertgen’s family chose a path of grace and remembrance. Surviving parents David Smith and Debra Ann Hertgen, along with eldest brother David, released an obituary expressing enduring love for both lost sons.

​The family remembered Matthew as a “caring and loving person” before his mind was overtaken by disease.

​”During his later years, Matthew struggled with severe and profound mental health issues; yet he expressed sorrow, remorse, and repentance in many ways,” the family wrote. “He departed with the love, friendship and forgiveness of his family and the eternal hope of salvation. May he rest in peace.”

​In memory of the brothers, the grieving family has requested that donations be directed to NAMI Mercer, a non-profit organization dedicated to supporting individuals and families shattered by severe mental illness.