The Rewe supermarket in the state of Brandenburg closed at 10 pm on Tuesday, and the store's manager was the only person left in the building when the roof collapsed shortly thereafter. The accident was almost completely silent.
The manager, who was tallying up the days' sales, was shielded by a supporting wall when the 1000-square-metre roof spontaneously gave out.
Fire fighters freed him uninjured.
City building authorities have closed off the supermarket for inspection and are trying to contact the builder for interviews.
“I have never seen something like this, where the roof falls in on itself,” building department head Harald Höhlig said.
The supermarket is located in popular shopping centre Akazienhof, near the Falkensee train station just outside of Berlin's Spandau district.