In the steady rain, lit up by N.Y.P.D. spotlights, the hushed site could have been a movie set—someone’s idea of a New York City calamity. “It looks like 9/11,” Novella Spence, a witness to Wednesday’s tragedy, told Curbed. “There was mist from the crumble, and the side of the building was gone.” 1321 Flatbush Avenue, which had stood since 1930, most recently with a façade of dusty white brick, housed a medical-uniform-and-supply store on its first floor and two floors of apartments above.