The department said it has retained an outside, third-party investigator to "gather the facts, interview all parties involved, and determine whether officers conducted themselves in adherence to department policies and guidelines".
Shaquille Dukes, 24, was walking outside a northern IL hospital in a hospital gown while still attached to an IV machine when he was approached by security, which then prompted an unnecessary confrontation with police that led to his arrest and the arrests of two other men alongside him.
Dukes said he's filed a complaint with the city, and according to his Facebook post, is working with an attorney.
Freeport Health Network (FHN) Memorial Hospital has not commented on the incident, calling it a police matter. Dukes said doctors had suggested he go for a walk and a hospital security officer accused him of trying to steal the IV stand to sell it on eBay.
The man alleges that when he told authorities he was being treated for pneumonia and asthma, an officer said to him, "I don't care why you're here, you're going to jail", and proceeded to transport him. "Can I help you?' but 'Are you stealing this?'" Dukes said his boyfriend began recording the encounter, as Dukes was trying to explain to the security guard that they were on a walk.
According to the police report, the security officer called police when the three men shouted at him and approached him in what he believed was a threatening manner. He said the guard told police, "I have three black males attempting to steal medical equipment from the hospital".
The racism allegation prompted Freeport's city manager to ask a police chief from another community to investigate the incident in which Dukes was charged with misdemeanor disorderly conduct.
The other two men were charged with disorderly conduct as well as resisting a peace officer.
Police chief Todd Barkalow told ABC News that it had been determined that Mr Dukes "was likely not trying to steal any of the property", but he and two other men were arrested "for disorderly conduct" towards the security guard.
Mr Dukes says his IV was removed - "not by a doctor" - as police officers stood by.
While officers were taking him to the police department, Dukes said he suffered an asthma attack.
Dukes said he was kept in the back of the police auto until paramedics arrived.
The police department told ABC News that per their investigation, "at no time did any doctor or nurse give that patient or any patient permission to leave the hospital while still hooked to an IV machine".
Freeport police say their officers acted "the best way they could", but have launched an independent probe.