An ex-NYPD cop fired last year for pulling his gun during an argument over a parking space has now been busted for vehicular manslaughter on Long Island, authorities said Monday. Aaron Cooper, 26, was charged Saturday with manslaughter, vehicular manslaughter and DWI for a blood alcohol level of .018, according to court papers. Cooper, who admitted he had been drinking, was speeding in a 2023 Toyota on Rosedale Road near Lawrence Court in Valley Stream when he crossed the double yellow line and hit a curb and pole about 4:30 a.m., police say. His car flipped over from the impact, killing his p…