Quintin Henderson, 28, was set to be released from the Cook County jail on May 2 "for a narcotics charge when he provided his personal information to Jahquez Scott for a promise of $1,000,' the sheriff's office said in a statement.
"Scott, 21, wearing a mask, then used Henderson's full name and personal information to pose as Henderson and left custody on Henderson's I-bond," the statement said.
"Jail staff learned there was a discrepancy when they did not have Henderson's paperwork when he provided his information for discharge," the statement said.
"An internal investigation is being conducted, and a search is underway for Scott," according to the statement.
Scott originally had a $50,000 bond for "an unlawful use of a weapon charge and was ordered to electronic monitoring if bond was posted," the statement said.
Henderson has now been charged with aiding escape "and was ordered held without bond for violation of bail bond on his original narcotics case," the statement said.
Calls to the Cook County Public Defender were not answered. CNN has been unable to confirm whether Scott or Henderson retained private counsel.