A New Jersey man who was recently found not legally responsible for the gruesome 2025 killing of his younger brother and a cat has died in custody.
Matthew Hertgen, 32, was discovered dead in his cell at the Mercer County Jail on Friday, May 8, in an apparent suicide, the Mercer County Prosecutor’s Office confirmed. The exact cause of death is currently awaiting autopsy results from the Middlesex Regional Medical Examiner’s Office. This was not Hertgen’s first suicide attempt; the Wesleyan University graduate previously tried to take his own life in February 2025, just a week after his initial arrest.
His death follows a March court ruling where a judge determined Hertgen was legally insane and not criminally responsible for the February 22, 2025, death of his 26-year-old brother, Joseph Hertgen. A hearing had been scheduled for May to decide his long-term custody and psychiatric placement.
During court proceedings, forensic psychologist Dr. Gianni Pirelli testified that Hertgen suffered from a documented history of severe, escalating psychotic behavior. According to court testimony, Hertgen experienced apocalyptic, religious delusions, occasionally believing he was God or the anti-Christ, and that a “sacrificial murder” was required to save the world.
“Anytime he closes his eyes, he’s seeing tremendous visions,” Dr. Pirelli testified.
The original charges stemmed from a violent attack inside a Princeton, New Jersey, apartment. Prosecutors alleged that Hertgen used a knife and a golf club to assault his brother, removed and consumed his brother’s eyeball, and set fire to a resident cat. Investigators later recovered a blood-smeared plate, utensils, and a cup filled with blood from the scene.
The family had long been aware of Hertgen’s deteriorating mental state. David Hertgen, the older brother of the two men, told investigators that Matthew had battled severe mental illness for five years. On the night of the attack, David texted Joseph to warn him that Matthew was experiencing “terrifying visions” and offered assistance. Joseph replied, “Will do,” hours before he was killed.
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Before his mental health declined, Hertgen was a standout student and athlete. He played college soccer at Wesleyan University, graduated with a bachelor’s degree in microbiology and biochemistry, and later worked as a vice president in finance for a telecommunications firm.
In an obituary published by his family, loved ones chose to remember his early life while acknowledging the severe illness that defined his final years. The family requested that donations be made to NAMI Mercer, a local mental health support nonprofit.
“Growing up, Matthew is remembered as a caring and loving person,” the family wrote in the obituary. “During his later years, Matthew struggled with severe and profound mental health issues; yet he expressed sorrow, remorse, and repentance in many ways. He departed with the love, friendship and forgiveness of his family and the eternal hope of salvation.”
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