At least 10 people were reported dead after a mass shooting at a supermarket in Buffalo, New York, Saturday afternoon. “Multiple people” were struck by gunfire, local police said.

 A tweet from Erie County executive Mark Poloncarz read that Buffalo police responded to the scene of an “active multiple shooting event” at the Tops Markets on Jefferson Street in the city.

“BPD on scene of a mass shooting at the Tops in the 1200 block of Jefferson Avenue,” the Buffalo Police Department tweeted. “Police say multiple people have been struck by gunfire. The shooter is in custody. Motorists and residents are urged to avoid the area.”

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A suspect is in custody, police said, adding that his condition was not immediately clear.

It is believed that the gunman entered the supermarket shortly after 2:30 p.m. and fired a rifle.

New York Gov. Kathy Hochul said on Twitter she is “closely monitoring” the shooting, and that her office has offered assistance to local officials.

Buffalo is New York’s second-largest city, with a population of more than 278,000 people. 

“It’s like walking onto a horror movie, but everything is real. It is armageddon-like. It’s so overwhelming,” a police official at the scene told The Buffalo News.

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A 106-page online manifesto, believed to have been uploaded by the shooter, explained that he was motivated by a conspiracy theory that white people are being replaced by other races. In the document, he says he is 18 years old and a self-described white supremacist and anti-semite.

“If there’s one thing I want you to get from these writings, it’s that White birth rates must change. Everyday the White population becomes fewer in number,” the document says. “To maintain a population the people must achieve a birth rate that reaches replacement fertility levels, in the western world that is about 2.06 births per woman.”

This is a developing story.