Onlookers may have thought that the intense police action was part of the plot, but when Hungarian police and a SWAT team descended on the set of Brad Pitt's film "World War Z" on Monday, it was not a scripted event.

According to US Weekly, the SWAT team raided a Budapest warehouse where weapons were being stored for use in the epic zombie flick, with anti-terrorism officers seizing 85 guns. The firearms, which were supposed to be nonfunctional, were automatic, military-style assault rifles that were in good working order.

The guns were confiscated at an airport near the film's set, where they were being stored.

"This morning a private plane brought guns wrapped in a parcel from a company to an individual [in Budapest]," said the director of Hungary's anti-terrorism unit in a statement. "Guns like these are highly illegal to transport even if they were to [be] used as stage guns, which hopefully they weren't."

A source told the magazine that Pitt — whose Plan B Entertainment is producing the movie set for a December 2012 release — isn't to blame for the prop snafu. "The movie company's employees must have made a mistake bringing the guns in without the Anti-Terrorism Unit's permission," said the unnamed source.

The movie, which is being helmed by Oscar-nominated director Marc Forster ("Machine Gun Preacher," "Stranger Than Fiction") and is based on a beloved novel by Max Brooks, stars Pitt as a United Nations employee who is traveling the world in an effort to stop a zombie plague from wiping out humanity. Forster has promised that he is taking a different approach to how the zombies move in the film from how they lurch in the book.

"In Max Brook's book they move in the George Romero ["Night of the Living Dead"] fashion. I feel like we have a little bit different approach," he revealed. "But it doesn't exclude that they might not eventually be fashioned [on] how George Romero's zombies move, it's just a little bit different approach. I think that will probably be the biggest discussions that there will be."

Check out everything we've got on "World War Z."

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