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A party advertised on social media drew as many as 300 young people on Saturday night to a public housing complex in Manhattan’s East Village, where residents said partygoers paid $10 to enter a basement room usually reserved for tenant meetings.

The music was blasting as the crowd, which included teenagers from an elite public high school in Brooklyn, spilled into the courtyard. Barely an hour had passed before residents of the development, the First Houses, called the police at about 10 p.m.

But someone upstairs had decided to do something about it. White paint and a caustic chemical were poured from overhead, burning at least 10 of the teenagers in the courtyard, the police said on Sunday.

Residents described a chaotic scene.

“I heard a huge ruckus and when I looked out the window I saw a ton of kids below,” said Chaz Rosario, 30, who lives on the fourth floor. “I hadn’t seen anything like that here before. I didn’t know what was going on.”