OOPS! The set of Brad Pitt‘s upcoming zombie movie, World War Z, was raided in Budapest Monday by a team of Hungarian police and a SWAT team looking for real weapons.

The raid resulted in the seizure of 85 fully-functional weapons, most of which were automatic, military-style assault rifles, stored in a warehouse on set. The weapons were supposed to be nonfunctional prop guns, but turned out to be fully working military-style assault rifles.

A source told US Weekly that Brad’s Plan B Entertainment production company simply made a mistake. “The movie company’s employees must have made a mistake bringing the guns in without the Anti-terrorism Unit’s permission.”

The director of Hungary’s Anti-Terrorism Unit said: “This morning a private plane brought guns wrapped in parcel from a company to an individual [in Budapest]. Guns like these are highly illegal to transport even if they were to be used a stage guns, which hopefully they weren’t.”

This can’t be welcomed news for Pitt whose film, per an US Weekly source, is “Already over budget and over schedule.”