A man was arrested this morning after injecting tetramine, a substance used in rat poison, into paper cartons of Wanglaoji (王老吉) at four supermarkets in Dongguan. One person was killed and four others hospitalized after consuming the tainted liquids. Two of the victims, a woman surnamed Xu and her brother, drank two cartons of Wanglaoji from a local convenience store yesterday afternoon and experienced vomiting, nauseousness and seizures. The two were both sent to…