EVERETT -- It is one of the most iconic images of the 9/11 attacks -- a photo of an American flag being raised by three New York City firefighters over Ground Zero.

That flag disappeared just a few hours after the famous photo was taken. Now, though, it has been found -- In Everett.

It was November 4, 2014. A man known only as "Brian" came to the front door of Everett Fire Station 1 holding a plastic bag. He told firefighters inside it was the Ground Zero flag and that he had been given it by someone who worked for NOAA in recognition of his service.

"Brian" said he was a local Marine Corps veteran of the Iraq war. He said little more, except he wanted the flag returned to its rightful owners.

Firefighters turned it over to police and the lost and found investigation of a lifetime was on.

"Well, it was a little overwhelming," said Everett Police Chief Dan Templeman. "One you get past the initial shock, it's time to go to work."

Templeman gives all the credit to his detectives who enlisted the help of the State Patrol crime lab. They analyzed DNA as well as dirt and dust samples from the flag.

Everything pointed to Ground Zero, but investigators still weren't 100 percent sure.

Detective Steve Paxton admits he was skeptical the flag was authentic. He analyzes photographic evidence for the Everett P.D. He remained unconvinced until he compared video of the flag being assembled and raised on 9/11 to the flag in his possession.

Paxton said it wasn't so much the flag itself, but the homemade hardware used to hoist it that caught his attention. It was rigged up with nylon rope and electrical tape. The tape was wrapped around the rigging 16 to 18 times. Paxton determined the video and the flag in question matched up.

"It's just one small piece of the puzzle. It isn't conclusive by itself, but when you put it in context with everything else we know, it's compelling," he said.

The final piece of the puzzle remains unsolved. Who, exactly, is "Brian?"

Shortly after police started their investigation they released a sketch of the man simply saying he had knowledge of some "found property." Nothing turned up.

They still have no idea who he is, or how he came to possess the cherished piece of American history.

For Chief Templeman, he's simply proud his department was able to return Old Glory to its proper keepers.

"It means so much to law enforcement and the military and our firefighters, we're just glad to have it back."

The flag was unveiled at the 9/11 Museum in Manhattan Thursday where it will remain on display.