Yashesh Desai, who had a history of psychiatric problems, was arrested on charges of killing his 47-year-old father Sanjiv Desai after police were called to their western suburban home of Woodridge just after 3 a.m. local time on August 14.
Yashesh's younger brother, who had called the police, told dispatchers, "My brother just killed my father," State's Attorney Robert Berlin was quoted as saying by the Chicago Tribune.
Officers found the brothers and their mother outside when they arrived, and Yashesh had blood on his hands and clothing, authorities said.
Yashesh "killed" his father with the lawn tool when the latter was sleeping on a futon. The father died in his sleep from severe head trauma sustained in the attack, the report said.
Yashesh was held on a USD 2 million bail following the attack.
DuPage County Judge John Demling approved a request from Assistant State's Attorney Helen Kappas that Yeshesh undergo a psychological examination.
Prosecutors said Yashesh had been seeing a psychiatrist and taking drugs usually prescribed for a major depressive disorder.
Yashesh told police at the time of his arrest that his father owed him money and that he struck him in the temple, Berlin was quoted as saying.
But later, in his police interview, according to Berlin, he gave nonsensical responses and spoke about Godzilla, the Turks, X and Y chromosomes, "as well as the need for 23 million soldiers." He also blurted out odd responses during his bail hearing next day.
According to the Chicago Tribune, when the judge asked Yashesh when he last held a job, he loudly responded, "The beginning of time."
Prosecutors said the accused had been living at home since he was dismissed from the University of Illinois at Urbana-Champaign in September after he had waved a knife at a student and was arrested for aggravated assault.
Yashesh majored in chemical and biomolecular engineering and left the school in summer 2010, the newspaper said.
Neighbor Kirk Tolliver, 84, said he would often chat with the son and the father. "They were always interested in national and world affairs," he was quoted as saying.
"The son was a smart kid, but he seemed a little depressed lately because he was having problems finding a job."