Being the first person to arrive at a party is always awkward. Being the first person to arrive in costume to a "zombie crawl," and getting arrested because people think you're going to shoot them is, well, REALLY awkward.
But apparently, someone thought a masked gunman was walking into a store, and called police. Witnesses say a dozen police cars converged on the scene and officers ran into the store, guns drawn.
Besides that annoying particulars of being arrested, you would have to think that being mistaken for a threat would be a cosplayers dream. I can imagine this guy yelling "It worked! it worked!" as he was cuffed and dragged into the cop car. It turns out that he was let go shortly after he was arrested when he was able to explain that he was in fact a dork in disguise and not "special commando HUNK" from the Resident Evil series. I wonder what he told his mom when he got home.