Surveillance cameras captured the entire theft on tape.
The incident happened around 4:30 p.m. outside the Rose Garden Chinese American takeout restaurant on the 1000 block of Susquehanna Avenue.
The repairman not only works on ATMs, but also refills them, police explained.
In this particular scenario he was fixing the ATM cash machine inside the store when two suspects, believed to be in their late teens to early 20s, made off with a black bag filled with cash from the worker's car.
The 27-year-old victim told police he left his 2007 Mazda 5 unlocked by mistake.
Sources say the man told police he was inside for about a half-hour when he remembered he hadn't locked up his car and clicked the locks closed remotely. But when he later checked, the bag containing $76,000 was gone.
Surveillance video shows the two suspects walking past the car and into a nearby store. They then exit the store and walk past the car a second time before going back, opening the door, and stealing the bag of cash.
The suspects fled on foot and were last seen traveling west on Susquehanna Avenue.