The sheriff's office said 32-year-old Richard Donta J. Cotton appeared for his hearing at the Leighton Criminal Courthouse around 12:30 p.m.
A judge remanded Cotton to custody on Possession of a Weapon with a Previous Conviction and Aggravated Unlawful Possession of a Weapon/Vehicle with a Previous Conviction charges.
But following the judge's decision, Cotton ran from the courtroom and left the courthouse, the sheriff's office said.
A warrant for Cotton's arrest was issued, and he remains at large.
Sheriff's police are actively searching for Cotton in with help from the Chicago Police Department.
Sheriff's police asked anyone with information to contact them at 847-635-1188 or dial 9-1-1.