A Princeton murder suspect, Matthew Hertgen, allegedly killed his brother, Joseph Hertgen, and a cat in their apartment. The surviving brother of the accused warned Joseph about Matthew's distress and visions before the murder. Matthew's mental illness was reportedly severe, and his brother spent time with him before the crime. The surviving brother texted Joseph about Matthew's struggles and invited him on a hike shortly before the murder. Matthew called 911 to report the incident, but details remain unclear.