The 50-year-old assistant state's attorney "might be injured very badly," an official could be heard telling prosecutors at the courthouse.
It happened on the first floor of the court, apparently after an argument spilled out from a courtroom into a hallway, witnesses said.
The man who choked the prosecutor told a bystander he did it because he was "sick of him mocking him," a witness said.
A Marquette District police officer confirmed police did respond to an incident at the courthouse, but declined to comment further.
Chicago Sun-Times, Sun-Times Media Wire