The preppy Princeton, New Jersey man who allegedly killed his younger brother in the family’s upscale apartment also set the family cat on fire during the attack, a law enforcement source tells The Post.

A 31-year-old man is accused of murdering his own brother and mutilating his body. Matthew Hertgen appeared in court in Princeton, New Jersey, via Zoom. Police found the body of his 26-year-old brother inside their wealthy parents' apartment.

A former college soccer star has been charged with killing his younger brother and a pet cat inside a New Jersey apartment complex near the Princeton University campus, according to officials.

A former Wesleyan University soccer player is accused of murdering his younger brother, himself a former soccer player at the University of Michigan, in a violent attack near Princeton University over the weekend.

Officers also found a bloody knife, fork and plate near victim Joseph Hertgen’s body, the source said — which has led cops to believe accused killer Matthew Hertgen, 31, consumed the missing organ.