A plate and utensils smeared with blood were allegedly found inside the home of a Princeton, N.J., man accused of killing his younger brother in February, according to a probable cause affidavit reviewed by PEOPLE. There was also a small cup filled with what appeared to be blood at the scene, the document states.

A detective’s affidavit described a gruesome scene when Princeton patrol officers arrived at the brothers’ apartment on the night of the killing.

Matthew Hertgen said he fell into a “fit of madness” the night his brother’s beaten body and the burnt remains their cat were found inside an apartment near Princeton University.