Credit: Gene Page/AMC Photo: A Herd of Walkers Crowds the Fence on The Walking Dead Season 4, Episode 2: “Infected”

Last week, several unsuspecting New Yorkers had the you-know-what scared out of them as they walked around Union Square. Unbeknownst to the general public, The Walking Dead’s network, AMC, enlisted the help of Relevant, a New York City-based ad agency, to devise a promotional campaign for the second half of the show’s fourth season, which kicked off last Sunday, February 9.

The epic prank the ad agency devised involved having several people dressed as walkers lurk beneath a subway grate and scare pedestrians as they walked by. The video of the prank (below) is pretty funny and certainly worth a watch, though the New York Post is now reporting that the hijinks are currently being investigated by the New York Police Department.

The MTA — the agency responsible for much of New York City’s public transportation — claims they didn’t know about the prank and that Relevant didn’t have permission to access the area beneath the grates. The MTA said via a spokesman on Sunday, “We are deeply troubled by this video. We have forwarded it to the NYPD and are also conducting our own investigation.”

Season 4, Episode 9 of TWD was watched by nearly 16 million people and beat out the Winter Olympics for the night, so we’re not really sure why AMC decided they needed a terrifying campaign like this in the first place, but Relevant’s CEO H. Tony Berger insists proper protocol was followed. “I can’t go into specific details,” he said. “But I firmly and strongly believe that what we did — the shoot— was executed legally and in accordance with city policies.”

PIX 11 reports that the MTA has since filed a formal complaint with law enforcement, and a police source tells the Post that “filming on city property without permits could result in charges of trespassing, criminal mischief and disorderly conduct.”

Yikes! Watch the video below and tell us what you think: Does the MTA have a case?

The Walking Dead Season 4 airs Sundays at 9 p.m. ET on AMC.

Sources: New York Post, PIX 11