Wearing all black, knee pads, a knife, grenade, a gas mask, and carrying what looked to be a machine gun, he walked into the Metro Clothing store Friday evening on Capitol Hill, which was sponsoring the zombie crawl to promote the Crypticon Horror Convention at the Seattle Center next weekend.
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.
"The police came in with guns and they caught the guy and I'm like, 'Oh wait, he's in costume,' " said Carl, the store's owner.
Seage, the event's organizer, says the man was dressed as one of the zombies from Resident Evil's Umbrella Corporation.
"I guess it was a little too good," she said. "It was too believable and that's why the police showed up."
The man arrested, who gave his name as "Jay," says he wasn't detained too long.
"It's definitely understanding -- they (police) weren't aware of the event going on," Jay said. "They just had to check me out (and they) let me go pretty quick once they saw what I was here for."
Seage said she was surprised it caused such a commotion.
"I didn't expect anyone to be arrested being dressed as a zombie because we did this last weekend," she said. "(There were) a dozen of us walking around in full zombie gear -- blood, guts and nasty skin hanging off and it just went fine."
Carl said the man was the first one to arrive in costume, and he could understand how someone might mistake the costume for something more sinister.
"It would definitely alarm somebody that didn't know what was going on," he said. "I feel so sorry for this boy."
Organizers said Jay won the top prize of the zombie crawl, which will get him a VIP pass to the Crypticon convention.