My 87 YO mother who lives by herself,once had her doorbell ring and door knocked on in the day. She does have steel security doors( first thing she did after fathers passing). Without opening the outer see through security she asked what he wanted. He never would give her a clear answer and kept saying "just open the door and I can tell you". She explained she didn't want any!! Still being persistent and not leaving she went to bedroom and retrieved a 12ga shotgun from wall. When he saw the barrel coming at him and her telling him to get outta here... He quickly took her advice this time.