The gunman has been identified by police in the city as 32-year-old Jason Nightengale and it has since emerged he made a number of sick online threats before the shooting.
As well as his four victims, two elderly women and a teenage girl have been left fighting for their lives after the horrific shooting spree in which Nightengale chose random targets.
Chicago police’s Supt. David Brown said he was only stopped by the “brave conduct” of officers after a parking lot shootout with cops ended in his death, reports the Chicago Sun-Times.
The killer had taken a woman hostage at a restaurant in the Evanston area of the city, as police rounded on him on Saturday afternoon.
He shot the woman in the neck before engaging in a shootout with cops in a nearby car park.
In the aftermath of the murderous spree, videos emerged on Facebook inn which Nightengale said he was out looking for victims. Another shows him driving and brandishing a weapon while talking incoherently.
Brown said the shooting spree began when Nightengale shot and killed a 30-year-old man, identified as a University of Chicago student, shortly before 2pm in a parking garage while the man was sitting in his car.
Nightengale then burst into a nearby apartment block and began “just randomly” shooting, hitting a woman and killing a building security guard who was sitting at the front desk, Supt. Brown said.
The evil gunman then left a 77-year-old woman in critical condition after shooting her in the head as she was checking her mail.
A resident in the block told CBS2 : “I guess the person wanted to use the phone, and I guess she was explaining to him he couldn’t use the phone, and he proceeded to walk into the building.
“I think she told him, like, he had to leave the building – and then he shot her.”
Nightengale then went to an apartment building in the 5500 block of South East End, where it is believed his relatives once lived.
He then forced a man he knew at gunpoint to give him the keys to a red Toyota, police said.
Nightengale drove to the 9300 block of South Halsted, where at about 3pm he entered a convenience store and announced he was carrying out a robbery.
He killed a 20-year-old man inside the store and left an an 81-year-old woman in a critical condition.
About an hour later, a 15-year-old was shot in the head while riding in a vehicle with her mum, leaving her in critical condition, Supt. Brown said.
Nightengale then returned to one of the shooting scenes and fired at investigating officers. No officers were hurt.
At 5:34 p.m., a dispatcher alerted Chicago police officers in Rogers Park that Nightengale was suspected of being there.
The dispatcher referenced the red Toyota that Nightengale had been driving and said the car “supposedly just pinged at 7600 N. Sheridan,” apparently regarding a tracking system in it.
The dispatcher said on the call: “He’s armed and dangerous — supposedly used a .45-calibre in two homicides today.
Moments later, an officer called the dispatcher saying shots were fired near the IHOP restaurant and Dollar General car park, where he was confronted by police and killed, according to the Chicago Sun-Times.
Evanston police tweeted a photo of a gun they said was recovered from Nightengale.
A woman, claiming to be his sister, wrote on Facebook: “My brother was not and hadn’t been in his right mind for a long time. My condolences to any families affected by his mental break.”
According to his LinkedIn account, Nightengale worked brief stints as a janitor, a taxi driver and as a “security investigator”, although the owner of the security firm said he’s never heard of him.