The incident occurred around 1:20 a.m. on the 1000 block of West Addison Street, between Clark and Sheffield.
A black male offender, possibly in his 30s, knocked the victim out - stole his cell phone - and rummaged through the victim’s pocket, said police.
The robber is approximately 5’9” with a husky build. He was wearing a plain white T-shirt and light-colored or beige cargo short pants with pockets on the side.
After the strong armed robbery, the violent thief fled westbound on Addison Street, according to an eyewitness.
At 1:29 a.m., police detained a possible suspect at a nearby McDonald’s at 3620 North Clark Street, between Patterson and Addison.
However, an officer at the fast food restaurant said the subject appeared to be in his 20s.
At 1:52 a.m., police confirmed the offender was still at large.
The victim was transported to Illinois Masonic Hospital in unknown condition.