(CBS) — An unarmed man suspected carjacking a vehicle at gunpoint died after Chicago police shot him during on the South Side Monday afternoon.

The man was shot around 1:45 p.m. when he turned toward officers with a dark object in his hand, police officials said. He was pronounced dead at Northwestern Memorial Hospital.

The dark object, it turns out, was not a weapon, police union spokesman Pat Camden said.

An officer gets “that mental image of somebody who takes a vehicle at gunpoint and later he’s reaching for something in the car — the picture is pretty well-painted,” Camden said.

Earlier, two officers on patrol in the South Shore neighborhood saw the man driving the gray Dodge Charge with out-of-state license plates, Camden said.

While a license plate check indicated no problems, an alert was broadcast seconds later describing a gray Dodge Charger with out-of-state plates taken in an armed carjacking, Camden said.

Camden said the officers followed the car and approached it on foot when it was boxed-in by traffic at a stop light near the corner of East 75th Street and South Jeffery Boulevard, Camden said.

After ordering the man out of the car, police say they saw him reach for an object with his right hand before opening the door and fleeing on foot, Camden said.

During the ensuing foot chase the man turned toward officers with what they incorrectly believed was a gun, Camden said.

The Independent Police Review Authority is investigating, Chicago Police News Affairs said.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2013. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)