The incident happened Monday evening at 6:15 p.m. inside the Shoprite supermarket on the 6700 block of Frankford Avenue.
The suspect was caught on surveillance shopping inside the store and placing 4 cans of baby formula into his basket.
When the thief tried to leave the store without paying, a 43-year-old male employee stopped him just outside the front door.
Click here to watch the surveillance video
The pair began to fight when police say the man pulled a syringe out and stated: "I have a dirty needle."
He then dropped the items and fled empty handed through the parking lot.
Police describe the suspect as a white male, 20-years-old, 6'0" tall and 170 lbs. with a thin build. He was wearing a white tank top, black jeans, black sneakers, and a black book bag.
Anyone with information is asked to call police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).