What hath Sully wrought? Every single goose—including the babies—was rounded up, put in crates, and gassed to death in Brooklyn’s Prospect Park last week. The geese—about 400 of them—were a signature of the park, and residents began to notice their conspicuous absence a few days ago. They mystery of their disappearance was solved Monday, when city officials, working with the federal Agriculture Department, admitted the birds were killed because they threatened human frequent fliers. The aim was to extinguish all goose populations within seven miles of major airports. Prospect Park is 6.5 miles from the La Guardia and JFK. Officials waited till the geese’s molting season—when the birds could not fly—to pounce. The birds were crated and then gassed with C02 at a nearby facility. Visitors, mourning the lifeless surface of the park’s lake, found zip-tie restraints among a scattering of gosling feathers.