Video shows the suspect throwing a freshly poured cup of hot coffee in the employee's face.
It happened at the Dunkin Donuts store located on the 4700 block of North Broad Street in the city's Fern Rock section Wednesday afternoon.
"There was a lot of yelling and cursing, he wasn't asking her how her day is going," said Lt. George McClay, Northwest Detectives.
The suspect wanted a coffee at discount.
"He has a coupon on his iPhone and apparently the girl doesn't accept the coupon because it expired," said Lt. McClay.
The suspect got enraged but still paid for his coffee.
The suspect and employee are seen arguing and the suspect appears to be leaving when something is said to set him off again.
That's when he comes back and hurls the coffee at the employee.
Now police are looking for him.
"This guy is from the neighborhood. He goes by the name 'Will,' he hangs in the area, he has been in the place a number of times so people know him. We just can't put a last name to him," said Lt. McClay.
The victim was not seriously injured and did not need medical attention but the suspect faces very serious charges of aggravated assault, and other related charges.