Chicago police confirm to PEOPLE that the 26-year-old's body was found at 6:37 p.m. in the city's South Side.
"Joshua Marks suffered a gunshot wound to the head and the manner of death was suicide," the Chicago Medical Examiner's office confirms to PEOPLE.
According to the Chicago Tribune, police responded to a call alerting them to a body discovered along a stretch of South Peoria Avenue, where Marks was found with a revolver nearby.
Police say two relatives and an acquaintance of Marks's were on the scene, and reportedly told them that he had suffered from bipolar disorder and schizophrenia.
In July, Marks was arrested in Chicago for allegedly assaulting a police officer.
At the time, the food star had reportedly claimed that MasterChef judge Gordon Ramsay had possessed his body and turned him into God. Marks was charged with aggravated battery to a peace officer and attempting to disarm a police officer.
Reporting by SANDRA SOBIERAJ WESTFALL and PATRICK GOMEZ