In February 2025, Hertgen carried out a brutal attack in their New Jersey luxury apartment, stabbing and beating his brother Joseph with golf clubs, ripping out and consuming his eyeball, and setting the family cat on fire, with Joseph's body found in a pool of blood beside a bloody knife.

About two months before his death, Hertgen had been ruled not criminally responsible for Joseph Hertgen’s murder due to insanity.

The grisly murder occurred in the brothers’ upscale residence, where 26-year-old Joseph Hertgen was killed and found with a knife nearby, described as a shocking crime scene.

Pirelli described ongoing delusions—visions that appeared when Hertgen closed his eyes—and a belief in a world-ending fate that he linked to a sacrificial murder."

Earlier, Hertgen attempted suicide in his cell a week after his arrest, prompting coverage that highlights crisis resources such as the 988 Suicide Lifeline for readers who may be affected.

The article provides information on mental health and crisis resources, including the 988 Lifeline and Crisis Text Line, for readers needing support.

Authorities noted the jailhouse suicide attempt by Hertgen occurred roughly one week after his arrest.

Hertgen’s obituary depicts him as a caring, loving person who battled severe mental health issues but expressed sorrow, remorse, and forgiveness to his family.

The obituary notes that his mental health struggles began in 2021 in New York City, traces his upbringing in a wealthy Toms River family, and recalls his time in the Michelle Mews apartments.

Family statements accompanying the obituary stress Hertgen’s loving nature and acknowledge his ongoing battle with mental illness, while expressing sorrow and repentance.

Testimony also noted Hertgen’s belief that he was linked to apocalyptic forces, sometimes seeing himself as Jesus Christ or the anti-Christ, influenced by Jung’s Red Book and the idea that a murder could save the world.

Forensic psychologist Dr. Gianni Pirelli testified that Hertgen suffered from schizophrenia with delusions and visions, including beliefs in prophecy and apocalyptic scenarios that framed his actions as sacrificial.