The incident unfolded at the 7-Eleven, 2821 N. Ashland, around 12:30AM.
According to police who reviewed surveillance footage, a masked man entered the store and struck the victim in the head with the butt of a silver semi-automatic handgun. He then took about $40 cash and six packs of Newport cigarettes before fleeing southbound on Ashland.
The suspect is described as a black man in his 20's wearing a white hooded sweatshirt, gray sweatpants, white gym shoes, and black gloves. He stands about 5'7" tall and weighs about 160 pounds.
An ambulance transported the clerk to Illinois Masonic Medical Center for treatment.
CPD case HY325490.