Investigators say they are looking for 42-year-old David Timbers in connection with the assault, which happened Tuesday morning inside a shop in West Philadelphia. He's wanted for aggravated assault.
Authorities say the clerk was burned on the arm after Timbers allegedly hurled the coffee at her.
Store surveillance video shows a man who claims to have paid for his sandwich, then takes the cup from the clerk's hand and throws it at her, eliciting a screech of pain. Others in the store confront the suspect but he makes it out of the shop.
Police say the clerk suffered severe burns in the attack.
Video of attack: http://bit.ly/JiICkK