The preppy Princeton murder suspect accused of slaughtering his younger brother — and feasting on his eyeball in a fight of rage — looked scruffy in court Monday as he learned his case would be heard by a grand jury. A somber Matthew Hertgen, the 31-year-old accused cannibal killer, sported an unkempt beard and an ill-fitting red crew neck sweatshirt during the brief Zoom proceedings in Mercer County Superior Court. He only voiced pleasantries such as “hello” and “thank you” to the judge, who indicated a grand jury will weigh indictment charges. His family was not in court. Hertgen’s next hearing is set for May 2. A former Wesleyan soccer player, Hertgen stands accused of using a knife and a golf club to murder his 26-year-old brother, Joseph, in the family’s ritzy Princeton apartment the night of Feb. 22. After the heinous deed, he ripped out Joseph’s eye and ate it, according to a law enforcement source. Sources said he also set the family cat on fire during his rampage, which happened just blocks from the Ivy League university’s campus. The Hertgen brothers were standout athletes who grew up in a $1.1 million home in Toms River before the family uprooted to the upscale Michelle Mews apartments, where units can go for up to $2 million. Officers discovered the grisly scene when Matthew called the cops himself to report a dead body and fire inside the Witherspoon Street home. A bloody knife, fork and plate were found near the victim’s body, a source said, which led cops to believe Matthew consumed his brother’s missing eye. A week after his arrest, Matthew tried to hang himself at the Mercer County Correction Center, sources said. Authorities still haven’t revealed a motive for Matthew’s alleged spiral into homicidal madness. But he’d been struggling with his mental health in the days leading up to the killing — David Jr. had texted Joseph just hours before Matthew exploded to tell him Matthew had been in distress, court docs said. David also told investigators his brother had been “extremely distressed, despondent and experiencing terrifying visions” before he allegedly flew into a murderous rage. “Wanting to help him, [the surviving brother] picked Matthew up at [redacted] at approximately 4:30 p.m.” according to a probable cause statement obtained by NJ.com. “[The surviving brother] and Matthew went to the grocery store and then to [the surviving brother’s] residence … where they remained until approximately 10:00 p.m.” Stay updated with the latest on the Hertgen’s brother murder case Princeton preppy murder victim received eerie warning text from other brother right before gruesome slaying Princeton preppy murder suspect’s devastated parents are no-shows in court as he’s repped by public defender in brother’s killing Princeton preppy murder suspect attempts suicide in jail after allegedly killing brother, eating his eyeball: source Princeton preppy murder suspect Matthew Hertgen appears for first time in suicide smock after allegedly killing, mutilating his brother David Jr. then dropped Matthew back at the apartment, where Joseph was also hanging out. He’d sent Joseph a text message telling him to reach out if he needed help dealing with their troubled sibling. “Will do,” Joseph responded — about an hour before he was hacked to death, the filing shows. After sending Joseph the warning, David also texted Matthew to invite him on a hike the following day and urged him to “Hang in there.” Less than 45 minutes later, Matthew called 911 to report his own twisted rampage, cops have said. The accused killer faces 30 years to life in prison if convicted of murder. A public defender has been repping Hertgen despite his family wealth — his dad, David, is the president and CFO of a multimillion-dollar tech company. Neither his parents nor his remaining brother, David Jr., showed up for Monday’s hearing.