A blizzard brought New York to a standstill on 23 February, with schools across the city closed. Restless young people without anywhere to go began to gather in Washington Square Park, summoned by Instagram chatshow Sidetalk, which wanted to stage an almighty snowball fight. A sea of young men in ski goggles gathered, armed with phones in one hand and balls of ice in the other. Cannonballs of snow flew across the sky. Others backflipped off snowmen or wrestled on the snow. The scene was of good-natured pandemonium.

“But it started getting chaotic once people were throwing gigantic blocks of ice. That’s when I left,” says Gabriella Yankovich who stopped by on her lunchbreak. “Boys being boys.”

Within an hour, there were 911 calls about teens climbing a park building and pelting those inside, and the New York police department increased its presence in the park.

But the dozen or so officers received an icy reception. They were swarmed and pummeled with snowballs. Social media was later flooded with images of snow raining down on officers.

What began as a viral stunt has snowballed into a larger, high-stakes clash between Mamdani and the NYPD that comes at a politically delicate moment. After winning the mayoral race in November, Mamdani announced he would be keeping Tisch as commissioner, despite her track record of increasing surveillance and shielding officers from discipline, at odds with the more progressive policies Mamdani promised. Political analysts said Mamdani kept Tisch on to assuage concerns that he would be soft on crime and against the police.