Citing police communications, the incident occurred around 8:45 p.m. in an alley behind the 3000 block of West Devon Avenue, near Devon and Troy.
Investigators said a black male in his 20s, wearing a black sweater with a red stripe and two large earrings, brandished a gun and stole the victim’s fur-lined coat and a black Samsung cell phone.
The thief was last seen running northbound on Troy from Devon, said police.
After the robbery, the victim, along with another male, ran to Devon Food & Liquor, 3044 West Devon Avenue, and asked for help.
At 8:54 p.m., police were searching for the suspect on the 6500 block of North Albany.
As of 9:38 p.m., the thief, who was apparently armed with a “glock nine,” was still at large.
According to an eyewitness, who spoke exclusively to Chicago News Report, the victim appeared to be 13 or 14-years-old.