The incident happened shortly before midnight Wednesday night at Chester Family Pizza on the 5500 block of Chester Avenue.
Click here to watch the surveillance video
Police say an employee was taking the trash out when a man with a gun approached him and demanded money.
When the employee told the suspect that there were three surveillance cameras throughout the restaurant, the suspect hit him twice in the head with the gun.
The gunman then grabbed a bag and ran off - but the bag only had trash inside of it.
He then fled the scene running south on 55th Street.
Police describe the suspect as a black male, 20 years-old with a thin build. He was wearing a black hooded jacket possibly a Northface, and black pants, and armed with a handgun.
Anyone with information is asked to call police at 215.686.TIPS (8477) or text a tip to PPD TIP a(773847).
You can also submit an anonymous tip online at PhillyPolice.com.