A photo seen on a local Facebook page has residents up in arms and the Mayor shocked and appalled.

The image was posted to the Parc-Ex Action Squad group Facebook page on May 1. The author said it was taken at the corner of Hutchison and Jean-Talon in Parc-Extension. It shows someone holding up a Nazi flag as demonstrators took part in the May Day protests below.

"I am deeply shocked by the hateful gesture" Mayor Valerie Plante said in a Tweet. "It does not reflect the values of inclusion and respect that are near and dear to Montrealers."

"Montreal is an open and welcoming city: Intolerance and racism do not belong here."

Mayor Plante was not the only city official to take notice.

Internet sleuths quickly determined the building the person was standing on was a condo building which needs a key to access the roof. The possibility of one of their neighbours being the individual behind the flag caused many of them to panic and demand answers.

The condo's board of directors is not revealing the identity of the individual but have contacted police and passed along the building's surveillance video to help with any type of investigation.

While Canada's criminal code does not specifically restrict owning or displaying a Nazi flag, sections 318-320 do provide law enforcement agencies the ability to intervene if a flag is used to communicate hatred in a public place.