The incident happened on Wednesday at about 4:35 a.m. at a Shell gas station at 401 South Larkin Avenue.
Joliet police said a man called 911reporting that someone was trying to kill him.
When officers arrived, they found a 39-year-old man with "erratic behavior," Joliet police said.
Police said they believed the man was under the influence of an unknown substance.
Officers then decided to detain the man and request and ambulance for medical evaluation.
The man fell while struggling with police; while on the ground, police put him in handcuffs.
Police said the 39-year-old lost consciousness and officers deployed Narcan.
The man was taken to the hospital where he died.
Police said there was no evidence that someone was trying to kill him.
The man's vehicle was found crashed into a tree in the 200-block of Emery Street. The investigation also revealed that the vehicle had struck a fence at 116 South Larkin Avenue.
The man has not been identified.
The officers involved were placed on administrative leave.
The Will Grundy Major Crimes Task Force is investigating the case.