Mainly children suffer from sever gastrointestinal distress because iron is corrosive to GI lining and due to that symptoms of nausea, vomiting(with blood in it hematemesis),bloody diarrhea.
SHOCKDue to excessive bleeding and fluid loss dehydration shock occur, difficulty in breathing and ultimately iron destroy our body tissue which makeup our organ because iron is toxic to cells wventully multiple organ failure, seizure ,coma and death occur.
TREATMENTTake to emergency where prompt treatment is life saving with gastric aspiration plus carbonated lavage ,fortunately there is an antidote deferoxamine IV but it is toxic too in high doses so better is prevention.
First thing to store iron supplements away from children (infect all medication store in child resistant cabinets). Don't take any extra by own always consult the doctor before taking. In any case of emergency take immediate to hospital.