The teenage gunman who allegedly opened fire on a crowded ice-skating rink over a pricey jacket — hitting two people, including a boy who may never walk again — was all smiles and swear words as cops hauled him from a police precinct Monday. “F— all you ni–as! It wasn’t over a jacket, it was over your mother, ni–a!,” a beaming 16-year-old Corey Dunton yelled at photographers outside the police Manhattan Midtown South police precinct.