A New Jersey man was in a “fit of madness” and experiencing “terrifying visions” when he allegedly murdered his younger brother, according to new details from the Mercer County Prosecutor’s Office. 

An affidavit released Thursday details the day Matthew Hertgen, 31, allegedly killed Joseph Hertgen, 26, with a golf club and knife in a Princeton apartment. Both men are former college soccer players, Matthew Hertgen at Wesleyan University and Joseph Hertgen at the University of Michigan. 

On Feb. 22, Matthew Hertgen called 911 and reported a fire and a dead body inside his apartment, telling dispatchers his brother had been dead for over half an hour. 

Princeton Police Department arrived on scene to find Joseph on the dining room floor with signs of blunt force trauma and a “large laceration to his chest and abdomen which exposed his chest cavity.” His right eyeball was not visible, according to police, who found the presumed murder weapon and bloody utensils nearby Joseph’s body. 

“Patrol officers observed a cup of what they believed to be blood, along with blood smeared eating utensils and a blood smeared plate on the dining room table…,” the affidavit reads. 

A cat was also found dead on scene with signs of burns and blunt force injuries. 

Matthew Hertgen, who had “abrasions and scratches” on his hands, told police he “went into a fit of madness.” He was then detained and transported to Princeton Police Headquarters where he declined to speak with detectives. 

A third brother of the Hertgen family told investigators he had been with Matthew Hertgen earlier that day, describing him as “extremely distressed, despondent, and experiencing terrifying visions.”

Upon dropping Matthew Hertgen off at around 10 p.m., the third brother saw Joseph Hertgen and later texted him to “contact him immediately if he needed any help,” according to officials. He also reached out to Matthew Hertgen telling him to “hang in there,” and invited him on a hike the next day. It was just over an hour later that Matthew Hertgen made the 911 call reporting Joseph’s death. 

Matthew Hertgen had suffered from “severe mental illness” for five years, the third brother told officials. A poem posted to his Facebook months before the murder describes knives, blood and pain. 

He now faces first-degree murder, third-degree animal cruelty, and several weapons charges. 

In a hearing at Mercer County Court Thursday afternoon, Matthew Hertgen voluntarily consented to pre-trial detainment. His next court appearance will be on March 24, according to the judge.