The surviving brother of Princeton murder suspect Matthew Hertgen sent a warning text message to his youngest brother about an hour before he was murdered.

Matthew Hertgen, 31, is accused of murdering his 26-year-old brother, Joseph Hertgen, in the family’s Princeton apartment, allegedly with a knife and golf club. He is also charged with animal cruelty related to the death of a cat.

Matthew’s surviving brother allegedly spent time with him hours before the alleged crime on Feb. 22, a Saturday, according to a probable cause statement obtained by Fox News Digital. 

The brother apparently told police that Matthew had “suffered from severe mental illness for the past five years.”

Joseph and Matthew Hertgen were star soccer players in high school and college. They were both athletes at Toms River High School, and Matthew went on to study at Wesleyan University in Connecticut. Joseph Hertgen was recruited to play soccer at the University of Michigan.